To share an experiment, with/without check valve

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Apr 6, 2008
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Hello All,

When I first got my back up pump + cartridge filter on trolley to clean my pool fast, I had the chance to experiment water flow loss with and without check valve. I think the one I was supplied is a lousy one. If it is a good unit, I don't think the loss will be this high.

I recall some valves are not full flow or the opening is not a 100% of the diameter of the pipe, I think this is the same I have for a check valve.

I think it will make a lot of sense to use a very good check valve even though it cost more, since loosing pump flow is like paying $$ for bigger pump but getting smaller pump equivalent flow.

Maybe use a bigger check valve and use a reducer, and we may get better flow.

This is a 1.5HP Pentair pump water flow without check valve installed on suction.
 

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This is with the check valve installed

I do not know the GPM loss. When I have a flow meter ( buying one ), I will update.

Hope this is informative in the visual sense
 

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I would suspect that it was a spring check valve and not a swing check valve.

Swing check valves usually do have an opening as large as the pipe but spring check valves do not. Also, spring check valves have a heavy spring which continually tries to close the valve increasing head loss considerable. Swing check valves are gravity closed so they have very little head loss when open.
 
On the Dot Mark......
Yes, its a spring check valve, not swing one... Let me check if they sell a swing one. I know brass swing check valves but usually I use small ones. The spring used is rather weak, but the opening is so bad, so small..... :evil:

Thanks for the info
 
Hello Dave,

My super pump can do 8 feet of prime said the Hayward website, I think that's the number.. However its so troublesome to fill up water all the time in the strainer basket, so check valve is what the builder put. I never try without one though but 7 feet vertical suction seems a bit far.

The last time the check valve stick a bit open, it took a long time to prime and messy...ha ha ha.

Thanks
Surya
 
Surya,

If your pump is primed and you shut the pump off, the water should stay in the pump basket and you should not need to re-prime each time you start.

If the water is draining from the pump basket each time you shut off, there is air leaking into your system.....most likely around the pump basket lid.

If you are unable to find that leak, then I agree that is way too much lift to require your pump to do each startup.
 
Hello Dave,

Water strainer always keep water, no leak but since the water must climb up 9 feet to the sand filter and 7 feet on suction, the pump impeller sort of run dry for some seconds. I don't like impeller running dry, pity the mechanical seal. I guess 16 feet of water in a 1.5" pipe needs more water than what the water strainer compartment can keep.

I will try one day by removing the plunger of the check valve, see what actually happens if all open like that.

Thanks
 
Surya,

As long as your circulating sytem is tight and no air leaks, there is very little additional work required for the water to "climb" nine feet because it is "dropping" nine feet to get back to the pool.

In fact, you could probably push water 100' as long as it dropped back 100' on the other side of the pump.
 

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Hi, Surya,

If your system is airtight, there will be only water in your pump on start-up....no air.

In other words, the pump will not require priming and can push the water as far up as you like.

It sounds like when you shut the pump off, the water starts to drain from the pump basket. That's an air leak somewhere in the system and, if you can find that, you wont need the pump to prime on start up.
 
stever said:
What is the Jandy Swing/Spring check valve? Is is a hybrid of the two? How does it rate relative to a swing only valve?

Thanks
Click to expand...

They are basically swing check valves with the addition of a spring so orientation of the valve is not important. They have the benefit of low head loss but do not depend upon gravity to close them.

Conventional axial spring check valves, typically sold in plumbing supply stores, should not be used in pool plumbing since they have very high head loss. Unfortunately, some pool plumbers still use these types of valves simply because they are cheaper and easier to find.
 
Also, the Jandy ones have a clear sightglass cover so you can see that it's working properly and visually inpect them. You can also repair them very easily.
 
duraleigh: having a check valve is a good idea in this situation (pump well above water level) for times when the pump strainer basket lid gets removed. The check valve will hold some water in the pipe, in addition to the water in the pump strainer area, which makes it simpler to prime after the lid is replaced. All of which is true even when there isn't an air leak.
 
Hello All,

Good thing Jandy check valve was asked, I think my friend has one under Pentair brand. He just emailed me the photo, looks like the Jandy thru on-line shops.

I will get that one for sure since it has lowest resistance.

This friend is a pool equipment supplier but not the one setting up my fixed mount filter system. I do not know him until after my pool was built.

In the USA a Jandy valve is asking US$40 or so. Looking at my photo of the waterloss using plunger type check valve, by right it should be banned, its wasting money and energy. I do not have a flowmeter yet to test what loss of water flow in GPM but by any logic, anything that creates such restriction is money down the drain. Save US$30 now over a cheapo plunger type check valve like what I have now, and pay a few hundreds $$ in long term loss. Whew !!! How come my pool supplier did not say that Jandy/Swing valve will be more efficient ? I will make lots of noise to my pool builder/supplier when I sort out the GPM loss using plunger type check valve over the Jandy and whatever loss my 1.5" pipe they installed for my 2.0HP Super Pump.

I don't understand my pool builder attitude. If one were wanting to save money, one will not be building a pool in the first place.


Good thing I know TFP, I learn more here.

Thanks All.
 
JasonLion said:
duraleigh: having a check valve is a good idea in this situation (pump well above water level) for times when the pump strainer basket lid gets removed. The check valve will hold some water in the pipe, in addition to the water in the pump strainer area, which makes it simpler to prime after the lid is replaced. All of which is true even when there isn't an air leak.
Click to expand...
Hi, Jason,

Yeah I sorta' agree. However, my distaste for check valves is deep!.

My pump is about 5 feet above the waterline and it's really tough to prime if there is an air leak or if I want to clean the basket. Instead of a check valve, I've got a 2" brass gate valve that I simply close when I turn the pump off and empty the basket. Of course, that won't work on a system where the pump is on a timer but mine is not and it's worth it to me to eliminate the check valve.
 
Dave,

The check valve in my balancing tank ( compensation tank ) is 5 feet below floor with a small opening and always 2 or so feet of water . So its going to be unpleasant to use manual hand operated valve in lieu of check valve.
 
Hello Dave,

I took a closer look at my pool plumbing. I can't avoid check valves. The balancing tank can suck my pool water thru syphon effect if there is no check valve. In this balancing tank, there is a pipe that goes to city drain if certain max height is achieved and it is lower than pool highest water line, because the balancing tank is in ground and same top height level with the pool. This balancing tank is for rain overflow or when an elephant took a swim and its body displacement will cause massive overflow... :p , just kidding on the elephant.

If I were to remove a check valve, I probably can remove the 2nd one 1 feet below the pump. This check valve if removed, the pump only need to suck a bit of air from pool main drain, which is only like 3 feet air gap or 3 feet height of pool water surface to pump impeller.

I think the PB wanted the suction pipes of the pump to be full of water at all times.
Let me play with that 1 check valve soon.

Thanks
 
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