Questions about foot (non return) valves

[BRCO]

I live in a condominium that faces the Indian Ocean. I have somehow got involved with oversight of our pool on the eighth floor. Previously I asked about replacing sand in the filter. Answers helped support exposure of a pervasive scam. This has more to do with a development where owners have to create documentation and find and expedite solutions.The questions:

No one knew a foot valve existed since it was located close to the bottom of the very dark balancing tank

at the end of the medium blue pipe as shown in the sketch. The location and inverted U pipework was obviously considered. Have we missed something?

Anyway the pool water is drawn into the balancing tank when the pump is off, so we are thinking of installing a new one with an extra shut off valve on the open pump area side of the tank wall to facilitate inspection and replacement.

Two questions then: Is this best location/configuration? What features should we look for in valves that might be available in Sri Lanka?

The level of the overflow has been raised with a standpipe from half way up to close to the top of the tank. We think this is wrong as the outlet from the gutter is 100mm and the overflow 50mm diameter. When it rains here, it comes fast and plentiful. Should we remove the standpipe?

 

[Jimrahbe]

B,

I suspect what you call a non-return valve (NRV) is what we call a "Check Valve". It just allows water to only flow in one direction..

I can't see any harm adding a check valve or NRV at the spot you indicated.. I like adding an additional manual shut off valve for maintenance.

I can't see where the original check valve or NRV location, in the main drain line, would make any difference at all..

If I understand your set up, the main pool has no skimmers, it just overflow all around the pool into what you are calling a "gutter".. It flows out of the gutter and back into the balancing tank.

When it rains hard, the pool overflow into the gutter and then into the balancing tank, causing the balancing tank to overflow into the overflow pipe. I am not sure the size of the pipe matters unless you have had problems with the overflow line not keep up and causing the balancing tank to overflow into the pump room. Seems if you lower the overflow standpipe, then the water in the balance tank will be less.. Someone raised the overflow for a reason, if the balance tank is not overflowing and causing an issue I would just leave it alone.

Thanks,

Jim R.

 

[BRCO]

I suspect what you call a non-return valve (NRV) is what we call a "Check Valve". It just allows water to only flow in one direction..

Yes in Blighty we call it non return; in Sri Lanka they call it foot, I think because they use them at the bottom of the ubiquitous artesian well pipes here.

I can't see where the original check valve or NRV location, in the main drain line, would make any difference at all..

Sorry the sketch isn't clear. Here is an amended enlarged sketch of the pipework in question:

I don't understand why they did it like this. Do you think it might create an airlock? I have no real experience with such occurrences.

Seems if you lower the overflow standpipe, then the water in the balance tank will be less.. Someone raised the overflow for a reason, if the balance tank is not overflowing and causing an issue I would just leave it alone.

I think what happened was the developers discovered the pool water returned to the balancing tank when the pump was off and water ran off to waste. Rather than check the foot valve, they capped off the overflow. During heavy rain, the gutter or channel overflowed creating a cascade down the side of the building and, if the wind was right, flooding the balconies of apartments below.

When we asked them to uncap the overflow, pool water returned to the balancing tank when the pump was off. This time the solution was to raise the overflow and cut down the flow from the pool. It wasn't until it rained particularly heavily, with tank and gutter already close to the raised overflow level, that the gutter overflowed again. These unthought-through solutions were initiated by marketing people who run the company. That is why I need to ask these questions.

It seems to me having the balancing tank half full is more than good enough to handle the overspill from swimmers and, as far as I know for backwashing, leaving sufficient volume above for backup water from the different sizes of gutter and tank overflows and rainstorm surges.

Sorry to be so longed-winded but it takes time to not only understand what has been installed and the competency of the workforce responsible, but to explain it!

 

[Jimrahbe]

B,

Ok, that makes a difference in my thinking... Logically, the only thing that makes the main pool drain into the balance tank, with the pump off, is gravity..

The foot check valve is designed to not allow water to flow backwards from the pool and into the balancing tank. It has to allow water to flow from the balancing tank and into the pump.

The vacuum line should have a spring loaded cap where it enters the pool.. If that cap is open or missing, that also could allow some water to leak back into the balancing tank.

Should be easy to test. Shut off the main drain, when you turn off the pump, and see if the water still drains back into the balancing tank.. If it does, the source of the water has to be the vacuum line. Either way, I agree that the problem is your current Foot check valve. Install a new NRV check valve would have the same effect of preventing water from flowing backwards and into the balancing tank.

If the pool works well with the balancing tank only half full, then that should be the level that it starts to drain into the overflow.. Kind of a balancing act.. You have to make sure the level in the tank works with the max number of members you expect in the pool at one time.

Your plans look like they should work to me..

Thanks,

Jim R.