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Scroll down to browse through some archived SWIMMING POOL questions and answers.  Please click the Pool Topics Link, on top of every page, to access a complete listing of Pool Problem subjects, an alphabetized Website Table of Contents, Pool Equipment Information, About Alan Biographic Material and a Pool Glossary. Use the other links to access additional subject information. More information about some new and unique products, for pools and spas, can be found by visiting The Website Store. You'll never know what you'll find and that's always fun. Be better prepared and avoid costly problems!

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How to decide, if a Heat Pump is the best heating choice, for a swimming pool? Heat Pumps are a very cost-effective method of heating a swimming pool. Akin to an air conditioner working in reverse, electric heat pumps extract heat from the air. Heaters represent a considerable investment and must be properly protected from the negatives effects of corrosion and poor water chemistry. Improper installation of a chemical feeder can lead to heat exchanger damage. Deposits of scale, due to excessive calcium hardness or poor water chemistry, can reduce the efficiency of the heater, by lining the heat exchanger with scale deposits.  If problems arise, refer to the Pool Problems Page, as a source of problem-solving information, broken down into various categories.  Scroll down the page and click on the linked keywords, catch phrases or images, in the archived answers below, to access additional information, on that topic or product.

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▼     Helpful, Problem-Solving Information, in a question and answer format.     ▼

Choosing The Right Heat Pump?

I had an inground pool installed last year and will be looking to install a heater, in the spring. I did some checking and came to the conclusion that a heat pump will be more economical to operate than gas or propane heaters. What should I look for in a heat pump? Thanks.

John H., Columbia, MD, 11/22/2016

There are a few important factors to consider, when evaluating for heat pumps. COP or Co-efficiency AquaCal Heat Pumps.Of Performance is similar to an Air Conditioner's SEER rating. Above 5.0 is good efficiency. Above 5.8 is very good efficiency.  Heat Exchanger Design is another important factor. While most inexpensive heat pumps use a copper heat exchanger, it is prone to damage from improper water chemistry or incorrect chemical treatment. This is, usually, not covered under a warranty. The AquaCal Heat Wave, line of heat pumps, utilize only Titanium Heat Exchangers, with a lifetime warranty against chemical damage. Evaporator Coil Design helps determine efficiency.  A single row of evaporators, versus dual row evaporators, are not as efficient. The more rows of refrigerant, flowing through the evaporator, the more heat it can collect from the air, which leads to a more efficient design. I hope that this information will help you make the best selection.

Sincerely. Alan Schuster, 11/22/2016

Where Should A Heat Pump Go?

We have an inground pool with an chlorinator (uses 7 oz. tablets) and a DE filter. The chlorinator is hooked in, just after the filter. We are planning to add an electric heat pump and are having a dispute as to where it should go. Can you explain the proper heater placement and settle the dispute. Feuding in Virginia.

Marty B., Chesepeake, VA, 6/25/2015

There's nothing to argue about! Put the chlorinator after the heat pump or you could destroy the copper heat exchanger (Not all heat exchangers are made of copper). The chlorinator must be last in line. The chlorine, in the chlorinator, is acidic in nature and could damage a copper heater core, if placed before the heater. Placement of the chlorinator at the end will result in warm water passing through the unit. You may have to periodically adjust the settings on the chlorinator, in order to match the rate of chlorine addition with the weather and pool usage. This is easier than replacing the heater! I personally know of someone, that had a heater installed by a plumber (unfamiliar with pools) and he installed it after the chlorinator: the heater did not last the season! You should be able to confirm this, by referring to the heater manufacturer's installation instructions. And don't forget a check valve between the heat pump and the chlorinator. Enjoy the warm water.

Sincerely. Alan Schuster, 6/25/2015

Heat Pump Practicality?

I am looking into adding a heater to my inground pool. I see a lot of material concerning heat pumps. Are they really practical for pools. I live in Vero Beach, Florida. Thank you.

Barbara F., Vero Beach, FL, 8/13/2011

As a matter of fact, heat pumps are very practical, especially in the sunbelt. In your location it should workAquaCal Heat Pump. out very well. There is a practical, if not physical limit, as to how much a heat pump can do in terms of raising the temperature. Check to see what that limit is and, consider, if you want to use the pool all year. It wouldn't be practical for year round use in New York, for example. In New York, it performs very well during the normal season and would be well suited towards extending both ends of the typical swimming season. In your area, it should be able to perform virtually all year. But, check it out to make sure before committing to a purchase. If you are interested in reducing operating costs, you might consider using a pool safety cover. These cover reduce evaporation, keep the heat in and provide safety for animals and kids. Good luck and I hope that I was helpful.

Sincerely. Alan Schuster, 8/13/2011

Heat Pump Suitability?

I think your site is great-very helpful. My question is, are the heat pumps suitable for use on Long Island, N.Y.  I have been debating on having one installed in my pool. Thank You.

Karen, Long Island, NY, 9/28/2010

A heat pump would not be practical to heat your house or an indoor pool, but it is very practical for use in heating a pool operated, in your area, for the typical spring to fall season. I hope that I have been of assistance.

Sincerely. Alan Schuster, 9/29/2010

Propane Or Electric?

Your site has been incredibly helpful and I am hoping you can help me with a couple of dilemmas we are having concerning the building of a pool. Should we go with propane or electric heater? This will be for an in ground pool in Tampa, Florida. I have been researching and it seems that propane is cheaper to run, but I am concerned about the safety of having a propane tank buried in the ground because of hurricanes etc. Gas is not being run in our development. What do you think is the safest, most cost effective, reliable, overall best option? We are environmentally conscious too, but safety has to come first.

Cheryl V., Tampa, Florida, 5/2/2009

I would choose an AquaCal heat pump, which is similar to an air conditioner running in reverse. It is more cost effective and is cleaner. You'll find data on cost of operation and performance. Good luck with your choice.

Sincerely. Alan Schuster, 5/2/2009

More Efficient Than Propane?

I'm considering purchasing a propane heater for my inground pool. I live in Massachusetts and would like to extend the swimming season. How would I use the heater, to keep the water temperature around 80F at all times. How long would I have to let it run, could it be regulated automatically, and what is the cost issue on using it in this manner? Thank you.

Mark J., Sharon, MA, 2/22/2008

Heat pumps work very efficiently, but as it gets colder, the efficiency drops. However, within the normal swim season for Massachusetts, the AquaCal heat pump will continue to operate very efficiently, depending on the volume of water. I am
The Circulator for all types of pools. assuming a swim season from the second half of April through the first half of November. What happens, when it gets colder, is the amount of time needed to maintain the temperatures increases. However, it will continue to heat down into the upper 40F. It may not maintain 80 during the very coldest parts of April to November, but it may maintain 70 - 75F, which may be good enough for comfort. The biggest benefit is that it can do this very cost effectively! Depending on your electrical costs and propane gas costs, the heat pump could save you as much as 89% over the cost to maintain 80 with a propane heater. I just saw the latest AquaCal unit at the Florida Pool and Spa show and it was incredibly quiet. Better circulation helps to distribute the heat and makes for a more uniform water temperature. The Circulator makes it all happen! Watch the video to see how it works! I hope that this information will help you make the right decision.

Sincerely. Alan Schuster, 2/22/2008

Solar Blanket Considerations?

I have two questions I hope you can help me with. My first question is, can you leave a solar blanket on a pool for a couple of days when you are not going to be swimming? I have been told that this will cause algae to grow. My second question is pertaining to turning my heat pump off at night. In the day my water temperature is 81 degrees in the evening I turn my pump to low speed which means my heater turns off. The morning temperature of my water is 77 degrees. Is it more economical to keep the temperature at 81 or to reheat the pool 4 degrees? Regards.

John, Toronto, Canada, 5/22/2009

There's no reason that you can't leave the solar blanket in place for periods of time. Just make sure that there are proper levels of sanitizer or there could be a greater possibility of algae growth, due to the warmer water. I once left it on for a week and returned to 93F and no signs of algae. The warmer the water - the greater the difference between the water and ambient overnight air temperature. In short, the warmer pool has more heat to lose. It would be more efficient to leave the heat pump off, with or without a solar cover. For more uniform distribution of the heat, adding The Circulator will make a positive difference. Enjoy the season.

Sincerely. Alan Schuster, 5/22/2009

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Defective Heat Pump?

I found your website and wanted to ask you a question. We are in the middle of purchasing a home in Florida that has an existing pool (inground/maybe gunite?). The pool and spa have severe staining, which we thought was algae when we originally saw the pool. On our home inspection, the pool was noted as "unsatisfactory". We met the pool company people that had been maintaining the pool and they informed us it was not algae, but severe copper, and that the problem has existed for a long time. They wanted us to be sure we knew it was in this condition when they began treating this pool. We decided to get an entire pool inspection. We contacted several companies and were informed that the severe copper is coming from the defective heat pump. We were future informed that IF we do not replace the heat pump, and have the pool acid washed or the finish resurfaced, the problem will continue with the new or clean pool because the copper is coming from within the heat pump because it is rusted inside. Does this sound like correct information, as we are supposed to close on this property next week. Can you help? Thanks.
Terry, Florida, 5/21/2005

Everyone is putting their own slant on things! Most likely the heat exchanger was not defective when purchased. The pool owners probably used chlorine tablets and failed to raise the pH periodically, as would have been necessary. This resulted in corrosion of the copper heat exchanger on a slow, relentless basis. Very likely, at some point, realizing the pH was too low, it was raised to 7.2-7.6. At this point the copper caused staining and discoloration. This was probably repeated more than onceAutoPilot Salt Chlorine Generators and here you are today. Probably, the pool will have to be resurfaced and the heat pump replaced. You have the opportunity to make better choices! For resurfacing, there are finishes that have great strength, are more chemically resistant and are great to look at. Today, you can get an AquaCal heat pump with a corrosion resistant titanium heat exchanger. While that doesn't give license to keep the pH low, it eliminates the possibility of copper staining. AquaCal is America's leading heat pump manufacturer. As long as I'm making recommendations, I might as well make some more. Chlorine tablets and low pH started this whole scenario. You might consider an AutoPilot salt chlorine generator. It will produce chlorine right in the pool, is highly controllable, produces better water quality and eliminates corrosive low pH conditions. And lastly, to help keep the pool clean, consider a Robotic Pool Cleaner. It will travel the entire pool removing dirt and acting as a second microfilter. I hope that this information will help solve the problems and get you off on the right track. Good luck with the house and the pool.

Sincerely. Alan Schuster, 5/21/2005

Tablets In The Skimmer?

Just had an inground pool installed with a heater.  We were given a "start up" package of Stabilized quick tabs (dissolve in 15 minutes, providing 59% of available chlorine) and was told by installer that we should use only these tabs daily and place directly in skimmer because of the heater.  I have seen on your site that the slow-dissolving tabs should not be placed in skimmer, but I wondered what other effective chlorinating options I have?  Is a chlorinator the way to go (installed after the heater) or are these quick tabs just as effective? Thanks.

Chris, 6/2/2008

The product that you are referring to is not slow-dissolving trichlor. It is a blend of trichlor and soda ash. This results in a fast dissolving tablet that is relatively neutral. Placing this type of tablet, in the skimmer, will not have the same negative impact on the heater. However, if the pool turns acidic, it will have a corrosive effect on the heater. Adding chlorine through the skimmer is never the best way to add chlorine. This type of tablet cannot be used in a built-in chlorinator. Placing these tablets in an enclosed chlorinator could result in a explosion. Only trichlor tablets can be used in an enclosed chlorinator. If you want to use an inline chlorinator, you must use trichlor tablets or sticks. The chlorinator should be last in line, after the heater, and must be installed according to the manufacturer's instructions. I hope that I have been helpful.

Sincerely. Alan Schuster, 6/2/2008

Too Much Heat?

We have a community pool of 120,000 gallons that is used mainly by seniors. We would like to keep the pool water at 87F maximum. It is hard to get consensus on a temperature, so this is what we settled on. Living in south Florida, the water can get into the 90's in the summer. How can we cool the pool down? Thanks for the help.

George R., Boynton Beach, FL, 6/1/2005

There is equipment available to cool swimming pools. It can all be done with a heat pump. AquaCal offers heat pumps that heat water, chillers that cool water and units that do both. Hopefully, this information will help make the summertime swimming more pleasurable.

Sincerely. Alan Schuster, 6/1/2005

Heat Pump Used To Chill The Pool?

I couldnt find any references on if and what is available to cool a pool. Ive seen a few products that claim to be able to cool a pool, but some look like gimmicks that are questionable to be worth the investment. Thanks
AquaCal Heat Pumps.
Harry, 7/21/2007

You have two basic choices: ice cubes or a heat pump with a chiller cycle. Heat pumps work by extracting heat from the air. There is nothing questionable or gimmicky, about a heat pump running in reverse. In the chiller cycle, it extracts heat from the pool. It is easy to drop the temperature from the 90's to the desired range, usually in the 80's.  AquaCal Heat Pumps is the industry leader, in this product category! I hope that you find this information cool.

Sincerely. Alan Schuster, 7/21/2007

Heat Pump And Salt Chlorinator?

I am installing a fiberglass pool and would like to install a heat pump in the system as well. My concern is I am also installing a Salt Generator and wonder if this will cause a problem with the heat pump because of the salt and rust. Also should I install an ozonator as well? Thanks for your support.
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Gene, 3/28/2006

Lots of pools have both. The concern with chlorine and heaters would be if the pH got below 7.0. With a salt chlorine generator, a low pH is very
unlikely and corrosion, to the heat pump, should not be a problem. An Ultraviolet Sterilizer in addition to the salt chlorine generator would allow you to lower the chlorine production and would extend the life of the salt cell. And it will make pH control easier. I hope that I have been helpful.

Sincerely. Alan Schuster, 3/28/2006

Titanium Or Copper Exchanger?

I'm in the process of buying a pool with a salt chlorinator and potentially a heating source (heat pump or gas heater). One dealer told me that I shouldn't install a copper piped gas heater with a salt chlorinator as corrosion would significantly shorten the life of the heater. He recommended a titanium piped heat pump which would be more resistant to corrosion. Another dealer said that the salt and chlorine levels were low enough not to impact the gas heater's lifespan significantly. Which on is right or are they both wrong?

Marc, Quebec, Canada, 3/29/2006
AutoPilot Salt Chlorine Generators

The titanium heat exchanger is superior in terms of corrosion resistance. Corrosion of the heat exchanger, in a pool with a salt chlorine generator, will only occur if the pH is too low. And that should be unlikely. Salt chlorine generators tend to cause the pH to rise and that makes low pH and corrosion very unlikely, barring complete neglect. You should find the heat pump more economical to operate than a fossil-fueled heater. I hope that this information will prove helpful.

Sincerely. Alan Schuster, 3/30/2006

How Can Acid Dissolve Copper?

At the beginning of the season, I had my water tested and amongst other things the dealer found a small amount of copper. I told him that I never used a copper algaecide - I only use the Polyquat Type. Because I have a heater and have a chlorinator with slow-dissolving tablets, he suggested that the copper came from having acidic conditions for a period of time. The water was treated and no problems resulted. My question is this. I'm no chemist, but I remember back in junior high school, we put a penny and a nail in strong acid and only the nail was attacked. If that is the case, how does acidic swimming pool water dissolve copper in a heater? Continuing my schooling. Thanks.

Shelly, B., Stony Brook, NY, 7/2/2010

Some memory. The teacher must have made a real impression on you. It is true that a copper penny will not dissolve in acids like hydrochloric or sulfuric, dilute or concentrated. However, a copper penny will dissolve in acids that are oxidizing agents. Your teacher might have demonstrated this by placing the penny in a nitric acid solution.  Hypochlorous acid is the active form of chlorine and it is an oxidizing agent. It, therefore, can and will slowly dissolve copper, if the pH of the pool water drops into the acidic range. Evidently, for some period of time, the pH in your pool was below 7.0 and this resulted in some heater corrosion. The chlorine product that you are using will lower the pH, as will acid rain and bathers. This will require regular water testing and pH adjustments. Your dealer did a good job and probably saved you from a bigger problem. I hope that today's "lesson" was successful. Enjoy the season.

Sincerely. Alan Schuster, 7/2/2010

Heat Pump Copper Corrosion?

Over the past three days I have been draining my vinyl pool to stabilize the copper build up. I had my water tested and it was off the scale for copper. I have notified the company that put in my heat pump, as the staff at the pool place are blaming the copper build up to the heat pump and visa versa. After three days of draining and refilling the water has changed from a turquoise blue to a light emerald green, please help me. The lady said to keep emptying until the water is clear again. I live in Florida and I'm afraid I will end up with a sink hole. There one is in our neighbors yard, but I need to clear out water. Thank you.

Vede L., 3/26/2009

Sounds like everyone's blaming some one else. Someone is at fault - the question is who? The corrosion of the copper heat
exchanger is the result of corrosion due to the presence of chlorine or bromine, combined with low pH Liquid MetalTrapconditions, the incorrect placement of a chlorine or bromine feeder before the heater, the lack of a check valve between the chlorine or bromine feeder and the heat pump or a combination of factors. Corrosion is not inevitable. The problem is not the heat pump, but how the pool was maintained or the equipment installed. Without the specific details, I'll leave it up to you, as to the actual cause of the corrosion. You should add a dose of a quality metal treatment, such as phosphate-free, Liquid METALTRAP for each 1.0 PPM of copper present in the water, as soon as possible. This should chelate (complex) the copper and help prevent staining and discoloration. Levels under 1 PPM are manageable, with proper treatment. By all means get the pH and total alkalinity optimized. Chlorine or bromine feeders must be last in line and should be separated by a check valve or installed as per the heat pump's manufacturer's instructions. Some heat pumps are made with titanium, instead of copper and are less subject to corrosion problems. Hopefully, the heater hasn't been destroyed. Good luck and I hope that I have been helpful.

Sincerely. Alan Schuster, 3/27/2009

Something Other Than Copper?

I recently destroyed my pool heater, as a result of corrosion. I was putting the 7 oz. tablets in the skimmer and it seems that the copper was corroded by the chlorine. I am not sure that I want to risk another heater. How can I avoid risking a repeat? It was an expensive lesson. Keeping my cool.

Irving S., Staten Island, NY, 8/2/2004

The copper heater core was not "corroded" by just the chlorine. It takes the combination of low pH and chlorine to subject copper to corrosion in a swimming pool. The practice of adding trichlor tablets to the skimmer is not something that I would ever recommend. Trichlor is very acidic and can slowly lead to corrosive conditions, if the pH is not properly maintained at 7.2-7.8. Installing an in-line chlorinator, after the heater and last in line, is a better way to add chlorine to the pool. There are heaters and heat pumps that utilize materials other than copper in the heat exchanger. Titanium and possibly stainless steel are used in some heaters. In addition, I believe that there are heaters that contain a chemically inert coating in the heat exchanger. These materials are less subject to corrosion. However, for the comfort of bathers and protection of all the metal underwater surfaces, you should maintain a proper pH. Solar blankets can be used with all types of heaters, not only to raise or maintain the water temperature, but to reduce operating costs. I suggest that you discuss heater options with a local pool professional, so far as heater choices and cost considerations. Good luck with your decision.

Sincerely. Alan Schuster, 8/2/2004

Choosing A Heat Pump?

Hi Alan, I have a 16x32 ft inground pool in Massachusetts. Just had a year-around  automatic cover installed. Am using an ionizer system, which uses electrodes-no chlorine ever. It uses 2 gallons of household bleach per week. Are there any contraindications for using a heat pump? Am leaning towards that rather than solar because of less maintenance. Am 65, live alone and want the most maintenance free product. Any suggestions or help is greatly appreciated.

Marianne L., Massachusetts, 3/15/2008

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There is no reason that you can't use a heat pump. AquaCal makes a complete line and they
include titanium heat exchangers, for longer life. When it will be too cold to use the heat pump economically, it will definitely be too cold for you to swim. The automatic pool cover is a plus, as well. On another note. I hate to be the bearer of bad news, but you are maintaining a chlorine pool. The ionizer is serving to minimize the chlorine required, but cannot not eliminate it. The household bleach contains 5-6% chlorine. You should try and keep the free chlorine level at 0.5-1.5 PPM. I suggest adding chlorine stabilizer, as it will help get the most out of the liquid chlorine (household bleach) that you are adding. A level of 25 PPM should be adequate. I hope that this information proves helpful.

Sincerely. Alan Schuster, 3/15/2008

Scale Deposits In A Heater?

I read somewhere that very high calcium hardness and pH can lead to scale formation and that scale can form on the underwater surfaces, including in the heater. My water has over 500 PPM of calcium hardness. I have a solar heater. I don't see any real evidence of scale. Every once in a while, I get cloudy water. Is there something I can do to avoid a potential problem? Please help.

J. M., 6/9/2008

A calcium hardness level of 500 PPM can definitely lead to scale formation and it can take place in your solar heater or any other type for that matter. If so, it will reduce the heater efficiency, by acting as a form of insulation. Make sure that you keep the pH closer to 7.2, than to 7.6. Try and lower the total alkalinity to within 80-120 PPM, if practical.  Stop all use of products containing calcium.  Add a quality Mineral Treatment, such as phosphate-free, Liquid METALTRAP, in order to help sequester the calcium, on a regular basis. This treatment can actually slowly dissolve scale deposits, over a period of time. There's nothing in your letter that positively indicates that you have a problem, at this time. But, some prevention does make sense. I hope that I have been helpful.

Sincerely. Alan Schuster, 6/10/2008

Check Valve Requirements?

Hi Alan, I have a gas heater and my heat exchanger just went out a few weeks ago (green corrosion). I replaced it. In case this was caused by chlorine, I installed a check valve on the output between the heater and my In-Line chlorinator. When I installed the check valve. I was unable to install it per the instructions. The instructions say you need 18 inches of up flow after the check valve in order for the weight of the water to keep the check valve closed. As you know, after the water leaves the heater there is not normally an up flow (it is all down flow from there). After 2 weeks of use, I pulled the return header off and found the new one is turning green on the inside. I had my water tested and everything was fine except hardness it was a little high (600ppm). But, the tap water in my area is pretty hard so I don't think there is much I can do about that. I doubt the hardness would cause the green corrosion anyway. So, my conclusion is maybe even though the check valve is spring loaded, it may be allowing the water to seep backwards due to there being a down flow. The only solution I can figure out is, come out of the heater and turn straight up for at least 18 inches. then turn straight down to get to my chlorinator. I don't know if 18 inches of up flow would work followed by an immediate 30 inches of down flow (This seems it might cause it to siphon). This does not seem like a good solution. I would also consider changing out the chlorinator to an off-line system, but I doubt that would help my situation. Do you have any suggestions. Thanks so much.

Jamie L., 9/5/2010

The green corrosion is being used by low pH conditions in the presence of chlorine. If your pool water has not been acidic for extended periods of time, that leaves only the check valve and the backflow from the chlorinator as the possible causes of the problem. Your solution seems to be workable. Any siphoning that might be created would direct the water to the pool and that will protect the heater from the corrosive backflow: the pool water being the lowest point. The check valve manufacturer's recommendation makes sense for their product and I suggest that you follow them. I hope that I have been of some assistance.
Sincerely. Alan Schuster, 9/6/2010

Check Valve Ups & Downs?

Hi Alan, I have a heater and my heat exchanger just went out a few weeks ago (green corrosion. I replaced it. In case this was caused by chlorine, I installed a check valve on the output between the heater and my In-Line chlorinator. When I installed the check valve. I was unable to install it per the instructions. The instructions say you need 18 inches of up flow after the check valve in order for the weight of the water to keep the check valve closed. As you know, after the water leaves the heater there is not normally an up flow (it is all down flow from there). After 2 weeks of use, I pulled the return header off and found the new one is turning green on the inside. I had my water tested and everything was fine except hardness it was a little high (600ppm). But, the tap water in my area is pretty hard so I don't think there is much I can do about that. I doubt the hardness would cause the green corrosion anyway. So, my conclusion is maybe even though the check valve is spring loaded, it may be allowing the water to seep backwards due to there being a down flow. The only solution I can figure out is, come out of the heater and turn straight up for at least 18 inches. then turn straight down to get to my chlorinator. I don't know if 18 inches of up flow would work followed by an immediate 30 inches of down flow (This seems it might cause it to siphon). This does not seem like a good solution. I would also consider changing out the chlorinator to an off-line system, but I doubt that would help my situation. Do you have any suggestions. Thanks so much.

Jamie L., 9/5/2007

Siphoning is not the issue. It is a closed loop system and there should be no siphoning. The issue is making sure that the check valve is closed. That is the purpose of the 18" inches of water. The weight of the water will make sure the valve is closed. Otherwise, there may not be a functioning check valve and the water from the chlorinator - high in chlorine and low in pH - can diffuse into the heater, by convection or due to density differences, and result in the type of corrosion that you are describing. That is why a closed check valve is important. I hope that this clarifies the issue and that the information has been helpful

Sincerely. Alan Schuster, 9/6/2007

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