Under Pressure - Pool Pumps and Solar Pool Heating Panels

Solar Panels And The Added Pressure on Pool Pumps

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A common belief is that solar panels add pressure to pool pumps, causing damage and premature failure. It simply is not a problem. This is an often-repeated myth perpetuated by pool service companies or dealers that sell traditional heaters (scare tactics).

Under Pressure - Pool Pumps and Solar Pool Heating Panels

Under Pressure – Pool Pumps and Solar Pool Heating Panels Work In Harmony

The thought process goes something like this: when using solar panels to heat a pool, you have to lift all of that water up to the roof. And there is a lot of extra plumbing added to the pool system. So this must make the pump work harder and will make it die an early death.

Here is what really happens, and why this is not a problem:

  • Water that is lifted to the roof also needs to come down. That water coming down creates a siphon effect, pulling the water behind it down. The higher the lift, the more the siphon creates a vacuum (negative) pressure, so the height does not matter much. The added pressure from height is negligible.
  • There is definitely extra plumbing involved in a solar pool heating system. However, at the recommended flow rate of about 40 gallons per minute for a typical system, the added pressure from friction in 2 inch PVC plumbing is not much. Some dealers use 1-1/2″ plumbing, which adds about twice as much pressure as 2″ plumbing. Larger plumbing mitigates this and results in a negligible effect on overall pressure. Less pressure (more flow) will increase your solar panel performance, but won’t make your pump last longer.
  • The panels themselves should not add much pressure to the system. Our panels have the lowest resistance to flow in the industry. But even our competitors’ panels will not hurt your pump. They may not work as well, but the pump should be fine.
  • Pool pumps are designed to work continuously along their entire performance curve. That means that as long as water is not nearly stagnant and there is at least some flow, the pump will not be damaged. Overheating is a potential concern, but that only occurs in a state of stagnation, which should not be the case because solar panels do not add much pressure as explained above.
  • Pool pump motors will not “work harder” either. Work (the physics term) is related to movement (displacement). If the pump does less “work” (i.e. moves less water) the motor will not “work” as hard. Pool pump motors operate at 3,450 RPM regardless of the movement of water in the pump. Pump motors die due to internal electrical failure or friction from bad bearings primarily. Heat is normally dissipated fine, but can be an issue if water stagnates due to high pressure. But again, this would not be related to a properly designed and installed solar pool heating system.

Solar pool heaters typically add somewhere between 1 PSI and 5 PSI to the pressure side of a pump. As long as the pump is not over-pressurized already due to a poorly designed pool or service issue, solar pool heating panels will not add enough restriction to cause pump damage.

To be clear, a high flow rate is critical to effective solar panel performance. Restriction is reduced by using large diameter plumbing, full-flow solar panel tubes with overmolded headers, quality full port valves, and good installation practices. But your pool pump is not at risk when adding a solar pool heater. The myth is simply not true.




  1. Question. My pool pump works fine with enough pressure when the water only goes from the filter back to the pool.. I maintain prime and the pressure at the returns is pretty strong. However, Within a minute of switching the water flow to the solar panels on my roof, my PSI gets really high and the water level in the pump basket decreases which then causes slight cavitation and greatly reduces the pressure at the returns. There are no leaks anywhere in the lines going to the panels, nor in any other panels, headers, etc. I have a Hayward 1hp superpump which has worked fine since we had the panels installed 2 summer ago but not now. I had a slight jam In my impeller which I freed up by getting some debris out. I’m wondering if the problem could be with the impeller but everything works fine as soon as the flow to the panels is shut off.
    Any ideas?

    1. Author

      Hi Tony,

      It sounds like you have a valve in the wrong position. It could be a solar feed isolation valve or possibly the 3-way valve if it is misconfigured. I have also seen some dealers install a return isolation valve (rather than a check valve), which is improper design/installation, but they continue to do it. I would have to see a picture of your valve positions to know for sure what’s going on.

  2. I have a problem not getting water to my rooftop solar panels for my pool I am running about 8 lb pressure and 2,600 RPM on my motor what is going wrong

    1. Author

      Hi Donald, unfortunately, that is not enough information to provide an answer. Those numbers might be just fine. It all depends on your particular pool. How do you know water is not getting to your panels?

  3. Hi we recently added solar panels 8 onto our roof . With a southern. Exposure . Our pool is approximately 25,000 gallons how many degrees should we see over ambient air temp. Our black flower bed reads 110 degrees so I am assuming my black roof is similar. However our pool is at best 2 degrees over ambient temp. I do not feel warm water coming out of the jets could the panels not be filling properly?

    1. Author


      There is no direct relationship between ambient air and your pool temperature when heated with solar panels. You need to compare your heated pool with an unheated pool. I don’t see you in our system, so you are probably not our client, but around here the Gulf of Mexico surface temperature is a really good indicator of unheated pool temperatures. Most solar pool heaters around here will get pools 6-12 degrees above the temperature of an unheated pool. You should not feel very warm water coming out of the jets – the water should be only slightly warmer. If it is much warmer, you probably don’t have enough flow through the system and you are not getting the performance you could. The best bet is to talk to your local installer who will have more information about your climate and your particular system.

  4. I have a 12×44′, 6′ deep end with 2 skimmers and 5 returns. Plumbing is all separate 1.5″ PVC coming together into 1 feed to the 1hp pump. When I added a suction vacuum, I had to shut one skimmer completely down for the vacuum to work. I changed the pump to a Hayward Super 3hp and have no problem with suction. Problem is, I get no heat from my roof solar heater now. I installed a 3 way diverter after the filter to the solar. If I divert 100% to the solar (which is how I ran it with the 1hp pump) my pressure goes up to about 12psi and I get no temp increase. With the smaller pump I could feel a noticeable temp increase at the inlet and in fact got the pool temp up to 95 in a matter of 2 weeks . If I try to divert only partial flow to the solar (to slow the flow down thru the solar) my pressure jumps to 15psi. With no flow to the solar I’m at about 10psi. Should I remove the 3 way diverter, install a Y or T fitting and a single ball valve to the solar? Or separate the solar from the filter and run a small booster pump just for the solar? I installed the pool and solar myself from a kit. Thanks for the help!

    1. Author

      Hi David,

      Your question is way too complicated to address accurately without seeing what’s going on, but generally speaking, you DO NOT WANT to have a noticeable temperature increase at the inlet. You want a high flow rate through the panels and a very low increase in temperature each pass through the panels. This will result in more overall heating. Temperature rise x rate of flow is what is important. And since there will be more heat transfer if the water inside the panels is much cooler than the surface temperature of the panels, more flow equals more overall heating (under typical heating conditions). We hear this all the time – my old pump/panels/system had warmer water at the pool jets… That’s BAD!!! It sounds counter-intuitive, but that’s the physics of heat exchangers, which is all that a solar panel really is.

      On the other hand, going from a 1HP to a 3HP pump (if not variable speed) can seriously damage your plumbing if pressures are not carefully considered. There are also safety considerations. Pools are engineered to use a specified pump and you should take care not to exceed building code flow velocities.

      The fact that you got your pool to 95 degrees at a different time of year is not comparable to conditions right now. Solar pool heaters do not guarantee specific temperatures. It’s all relative to current conditions, unheated pool temperatures, and weather conditions.

  5. I just had a solar pool heater installed. 6 panels on a single-story roof. Before the solar panels were installed or when they are bypassed I have two water feature waterfalls in my pool that work perfectly. When the water is diverted up through the panel’s only one side works. Is that an indication of insufficient pressure in the line, possibly due to the pump? The pump is 1.5 horsepower. The solar system is new but the pump is old

    1. Author

      Hi Dennis, I’m not sure what brand of panels you have or what plumbing size, but some systems have more restriction to flow than others. That’s why we use the panel brand with the least flow restriction and only use 2-inch plumbing throughout the solar loop with intelligent application of fittings to reduce added head pressure. With that said, you may be able to correct your issue using various techniques. First and foremost, make sure you have a NEW filter cartridge. This is the number one thing that causes system problems both initially and long term. A clean filter maximizes the flow throughout the system. Second, make sure all of your suction valves are wide open (except your cleaner port if you have one). Suction pressure robs your pump with the ability to create flow. Next, you may be able to adjust your pool return valves to redirect water to your waterfalls. This often involves restricting flow back to your pool jets so that your waterfalls receive more water.

      Regardless, dual waterfalls are always tricky. I don’t know why pool builders install them. Balancing the flow between two waterfalls can be problematic when flows vary. If (when) you replace your pump with a variable speed model, you will definitely have some frustrations in trying to get your fountains to work right. You will need an advanced controller to vary the pump flow rate for each scenario. This is true whether you have solar panels or not.

      The same issues occur when you have multiple laminar deck jets or multiple features like a waterfall and a bubbler. Variable speed pumps or other features like solar panels or heat pumps with bypass valves can cause headaches in trying to balance flow to these features when they are on the pool circulation pump. They might sound like a nice idea when you are building a pool, but they can become a real issue.

      You should also consider turning your waterfalls off, particularly when heating your pool (with any heat source). Waterfalls are massive pool coolers! You can do this manually, or with the right pool controller you can automate the valve(s).

      If you are in our service area, feel free to call our office and schedule a service call to take a look at your pool if your solar contractor can’t figure things out. It happens frequently around here.

  6. I have two 100 meter coils of black 1″ plastic pipe on my roof designed to help heat our 32′ L x 16′ W x 4.5′ D
    swimming pool in Yucatan Mexico (tropical beach climate). We use the 3/4 HP pool circulation pump to feed an existing 3/4″ PVC line to the roof. It’s about about 10′ vertical run up and 10′ horizontal run before transitioning to a 1″ pvc pipe on the roof that feeds the two 1″ black plastic piping rolls, 100 meters each, before returning to the return side of the pool circulating piping. I have a anti-reverse valve near the pool pump on the supply feed to the heating coils, and manual cut-offs on the 3/4″ supply and return lines connecting the rolls. I know it would be better if the lines between the 2″ pool piping and the 1″ coils were larger than 3/4″, but they were existing so I wanted to try using them to feed the coils. Can this cause any damage or problems? Any suggestions to improve this self-designed system? Thank you!

    1. Author


      You aren’t going to get anywhere near enough water through that system to effectively heat your pool. 3/4 inch pipe is only good for about 25 gallons per minute. The distance of your total plumbing will cause excessive head pressure and you will get very little flow. It’s a poor design. Pipe coils are pretty poor heat exchangers anyway. To answer your question, as long as you have some reasonable amount of flow through the pump (say 10 GPM) you will probably not do any damage to it.

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