The pool installer is giving a little pushback on installation of check valves at heater bypass and spa returns. His thought is that the check valves restrict flow and is not needed for the bypass. Said that since swcg is not producing chlorine when pump is off, there is no chance of high levels of chlorine back into the heater like a tab feeder. For the spa, if the water level drops to the returns, as soon as the spa is on it will fill back up. I’m not real happy with either of these statements. If there is truly a restriction at the check valve that effects flow, I feel like the restriction is not going to be much knowing that head loss is function of size and length.
New pool plumbing help
- Thread starter Lampasas1
- Start date
The spa should never be allowed to have the water drop down to expose plaster on a plaster pool so I don’t know why a fiberglass pool would have to operate differently. Clearly someone has figured out a check valve that works ok in that situation.
- Jul 21, 2013
- 65,164
- Pool Size
- 35000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
You have a builder who uses flex PVC and too small plumbing on the spa and now he is looking after your best interests cautioning you that a check valve restricts flow?
Those too small pipes restrict the flow more than any check valve.
Thanks him for his advice an tell him what you want on your pool and spa.
Except that is not the purpose of the check valve when used with a Heater Bypass - Further Reading
It is less of an issue then with a plaster spa. But in the meantime your spa surface is exposed getting dirty from air pollution.
There is just no reason for the spa to drain out when it can be fixed with a CV.
You are correct. The CV restrictions are a rounding error in the janky way he is already doing your plumbing.
- May 3, 2007
- 18,073
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
The last part of the statement is only true for straight pipe. Head loss in fittings and valves is primarily dependent on geometry.
In a check valve there is a spring loaded flapper that is always trying to close and if you ever look at one in operation, at high speeds it is open much more than at low speeds so proportionally, lower flow rates have an effectively higher plumbing curve than higher flow rates so efficiency is lost.
The check valve after the heater is useful if isolating the heater but I see no other functional purpose for it. A standard 2-way valve could be used instead for isolation as it is rarely required and has less head loss then a check valve and especially at lower flow rates.
So if I am bypassing the heater with a 3 way and no check valve, would the back pressure of water entering the outlet side of the heater potentially be an issue?
- May 3, 2007
- 18,073
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
If you don't want the check valve after the heater, I would put a 2-way valve there so that you can isolate the heater if needed.
Back pressure is not an issue because the inlet will always have higher pressure than the outlet. As I previously mentioned, I would setup the 3-way valve for two positions.
Position 1: The heater AND bypass are both open at the same time
Position 2: Bypass closed and heater open.
This way there is always water flowing through the heater. There is just less head loss when both the heater and the bypass are open (position 1).
Back pressure is not an issue because the inlet will always have higher pressure than the outlet. As I previously mentioned, I would setup the 3-way valve for two positions.
Position 1: The heater AND bypass are both open at the same time
Position 2: Bypass closed and heater open.
This way there is always water flowing through the heater. There is just less head loss when both the heater and the bypass are open (position 1).
- Jul 21, 2013
- 65,164
- Pool Size
- 35000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
Having two valves that need to be kept in synch sets someone up to deadhead the heater.
Someone will see one valve and turn it and not the other.
One 3 way valve plus a check valve is idiot proof.
- May 3, 2007
- 18,073
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
Take the handle off the 2way to prevent someone else from inadvertently shutting it off.
The 3way will be automated and most controllers will auto shutdown with dead head and an SWG flow switch. The Intelliflo will shut down on its own.
Plus, I would not hesitate to use a 2way as I am the only one who touches the equipment.
Also, I find check valves will start leaking a bit after a few years so are not all that great at isolation.
The 3way will be automated and most controllers will auto shutdown with dead head and an SWG flow switch. The Intelliflo will shut down on its own.
Plus, I would not hesitate to use a 2way as I am the only one who touches the equipment.
Also, I find check valves will start leaking a bit after a few years so are not all that great at isolation.