Check valve for my heat pump really needed?

[stbasil]

I just installed a heat pump for our pool, and it is about 15 feet away from the equipment pad, plus about 3 feet higher than the pump (the only reasonable location for it). Usually, a check valve is required on the outlet of the heat pump to prevent high concentrations of chlorine from backing up into the heater after the pump turns off. However, considering the distance and height, plus the fact that I have a SWG chlorinator, it seems like the check valve is not needed in my particular situation. I left it off, but can easily install it if I need to. Any thoughts from the experts?

 

[Bama Rambler]

Your system should be plumbed, pump > filter > heater > swg. If it is then the check valve is needed to prevent the high chlorine concentration near the swcg cell from backing up into the heater when you shut off the pump. The swcg cell also produces hydrogen during the conversion process.

 

[stbasil]

OK, yes the plumbing sequence is correct, and I understand the reason for the check valve. But it seems like the untreated water in the ~15 feet of 2" pipe (about 2.5 gallons) would dilute the excess chlorine, and also the 3 foot rise would probably prevent water movement back up to the heater anyway. Reasonable assumptions?

 

[Bama Rambler]

So the heater is 15' away from the swcg and 3' higher than the swcg? I'd still put a check valve in the line.

You have to think of the complete plumbing system. If you have to move water down 3' to get to the water level then you have had to move water up 3' to get to the equipment. The danger is that the piping could create a siphon effect once the pump is off and water could flow backward through the system. I know it's probably a remote possibility but the reason they recommend one is because it's happened before.

 

[stbasil]

OK--I get the idea. Thanks for your help!

 

[stbasil]

Well, now that I am looking at the schedule 40 check valve that I had bought at Lowe's, I can see that it is a spring-diaphragm type. I wonder about the flow restriction that this valve will create. So, I did a little research and see that there are lots of types of check valves, and the one I bought is probably great for a sump pump type application (it was also only about $14). Is it worth it to buy a $50-60 check valve from Jandy or Pentair, for instance? I have not found much information about flow restriction online--just some references to "full flow" check valves. Also, can the Jandy and Pentair models be mounted in a vertical position (online info does not say) like the cheapo one can?

 

[mas985]

What ever you do, don't use the check valves that you get at hardware stores. They have about 5x the head loss as a Jandy or Pentair check valve and will significantly reduce your flow. Spend the extra money for the Jandy or Pentair, it is well worth it.

I might get some grief for this but in my opinion, I believe that the recommendations for using check valves with SWGs is a carry over from the puck chlorine feeders. Pucks will continue to dissolve and the chlorine concentrations will rise much higher than what a SWG has left over after it is turned off. The chlorine rise of a typical SWG is only about 1-2 ppm and when shut off, they don't produce anymore chlorine unlike a puck feeder. So I think the recommendation is just to be conservative but if you really think about how a SWG works, I just don't see how the chlorine level could get that high with the pump off to damage the heater. Also, if you happen to have solar, the water will drain out of the heater towards the returns, so it isn't an issue in that case.

Some manufactures such as Goldline don't even recommend a check valve after the heater and add to that your SWG is 15' away from the heater, I would say don't bother. But if you want to be safe, go ahead and put one in, just make sure it is a flapper type of check valve. Also, if your heater manufacture requires it for warranty, then definitely put one in.

 

[stbasil]

Mark, you have addressed the issues that originally made me think the check valve was superfluous, especially in my application. Thanks for the additional inputs. BTW, I wish I DID have solar, but the 3.5 story height and our complex roof surface just made it impractical and expensive (and too dangerous for DIY), so I decided on a heat pump. We plan to run it sparingly, and we are using a solar blanket.