WaterNet Online

I have a negative edge pool with a chlorine generator that I have to add salt to every other week. I realize that water leaving the pool is the source of salt loss but checking for a leak reveals no water loss. I guess my question is about hydraulics of such a pool and whether it is normal for the autoleveler in the catch pool to add water everytime the edge pump cycles. As the catch pool is falling and raising the pool level the fresh water comes on and refills the catch pool with water. This influx of new water dilutes the salt concentration. The pool water level remains the same when the edge pump is stopped. No equalization(of course). Is this normal or is the catch pool sized wrong or what? The water leveler is a System Dynamics Levelor and the probe is at the lowest point in the system.

If you have an autoleveler (autofill)and it is working properly, how do you know you do not have a leak? Are you turning it off to determine that you do not have a leak? Pools are generally 'closed' systems and do not send any water to waste.

It would appear that you have a leak.

Rick Bays

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Rick Bays

I have already traveled that road and we repaired leak in catch pool and have checked the pool and catch pool w/o levelers on. I do leaks regularly and don't feel as though the system has a leak. Having said this I agree that there little else that could explain the salt loss. I guess this could be a good off season project.

Have you been checking the salt with a meter or AquaChek titration strip (AquaChek White)?
Rick Bays

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Rick Bays

When you pump switches off, does the water level in the main pool fall? If it does this indicates that you have a stuck non-return valve somewhere. When the pool backfills into the balance tank, it overflows and this is where you can lose water. When the pump restarts fresh water will top-up the balance tank to replace that lost, causing dilution.

rgds

Vaughan

I check the salt level with a Myron-l meter. The pool doesn't drain down after the pump shuts down but the catch pool will over flow via the water falling over the weir wall till the level drops below the edge. Should the capacity of the catch pool be sufficient to run the edge pump and cause an overflow which would refill the catch pool enough to sustain flow or is it normal for the catch pool to require refilling as the edge pump runs? This is how the system seems to be operating. Maybe the high (unusually)evaporation lately is a problem but the system has been operating in this manner since startup. We have adjusted the pool level to decrease the amount of water required to get the water over the edge and the water leveler in the catch pool starts to refill the basin before the overflow starts.

If there is no leak in the system (or pool)and all valves are working properly, you will not lose salt. End of story.

I think the problem here is one of 2 things.

The Catch pool is improperly sized, when you shut off the negative edge pump the water overflows the catch basin and goes out the drain that should be there. The water that overflows the catch basin is the water that is on top of the weir (negative edge) usually about 1/8".

If water evaporates the water will still retain the salt.

To rectify the situation you will need to either look into raising the overflow level, and/or lowering the autofill level.

When you tested for leaks, did you have the negative edge pump running? Its possible that there is a leak in the negative edge return line, or possibly even water falling off the weir, or wall.

You can try running the edge pump with the autofill off, but make sure you are around during this test. You can also put a water meter in the autofill line to track how much water the pool is using (never a bad idea with this type of pool).

Have all the autolevelers cut off now and its cold outside. Have some time this fall and maybe I can spend some more time with this problem. I think the undersized catchpool or much too high sensor could be at least part of the problem. I agree that the only way to lose salt is to lose water but so far I haven't been able to dectect the water loss. Incidently, ALD did the leak survey on the pool system so I don't know if he checked the return for the edge pump.

The catch pool should not overflow when the system is at rest. It should be of sufficient volume to 1. Draw down without until water falls over the weir to replenish the catch pool without causing any vortexing at the catch basin suction points. 2. There needs to be an overflow pipe at the top of the catch basin to remove large rainfall amounts. One of the most common mistakes in V Edge pools is improper catch pool sizing. You cannot make them too big. Unfortunately, fixing that problem can be very tricky hydraulically.

I know you said fix is tricky hydraulically, but what would be done to remedy the problem?

On 5/27/2006 4:02:05 PM, Ricky Kelley wrote:
>I know you said fix is tricky
>hydraulically, but what would
>be done to remedy the problem?
>


"very tricky" = impossible. Without increasing the size of the catch basin.

You can possibly lower the operating level of the catch basin to give it more room for the water on top of the weir.