Lowering water below returns versus keeping water level high for closing - pros/cons


LifeTime Supporter
May 4, 2010
I've been closing my pool the same way for the past 12 years. I chose this method because the first year, I had the pool company close the pool and this is how they did it. So I have no reason for doing it this way other than copying them.

I blow out the lines from the equipment side while the water level is normal. Then after the pool is closed, I lower to 18" below the coping per loop-loc requirements.

So, basically, I blow out the skimmers first using a ultra gizzmo (hole in top) and plug the top hole once it is only blowing air through. Once the skimmers are plugged with gizzmos the returns start bubbling (since they are still under water). I let them each blow for about 2 minutes and then plug with threaded plugs. Finally, the main drain blows bubbles and I wait a couple of minutes then shut the MD valve creating a vacuum. Then I open up the equipment plugs in polaris booster, heater and pump. Done

It seems to me that it would be much easier to do the closing without all the water getting in the way if I simply drained the water below the returns. Once all the water is purged (easy to see), just plug it.

The only advantage I see to leaving the water level at normal levels for the blowout, is that I can see any leaks in the plugs. small leaks caused by bad plugs, etc. would be hard to detect without the bubbles.

However, if I am diligent about keeping the water levels below the returns (at least until the water freezes), small leaks should not matter.

I would like to get some expert opinions about which method is best for blowing out the lines. Pros and cons of each way. I am seriously thinking of lowering the water below the returns this year for the first time, but am afraid to since I've had such good luck doing it at full levels since I've owned my pool.

Please weigh in on this and help me decide......

Thanks in advance


LifeTime Supporter
May 4, 2010
Some pools should be closed at normal operating levels. Pipes can be purged & capped below water.

High water tables & Liner over feature treatments should left at normal operating levels.

OK, so I have a liner pool with steel steps that the liner cover. If I lowered the water below the returns, the top 2 steps would not be covered with water. Is that what you mean?


Platinum Supporter
TFP Guide
Jul 30, 2014
Monmouth County, New Jersey
IMO, draining below the returns is overkill. Draining slightly below the skimmer (1"-2") helps clear the lines better. Most pools, if not all pools have thermal heat in the ground and it would take a very long cold winter before any damage can be done. Remove 80%-90% of all water in the lines and you can sleep comfortably. When in doubt, use anti-freeze.

I had performed a test with a 3" schedule 40 PVC in where the water was 90% full with a cap. No movement on the top (bottom sealed). The following year, I filled up 100% and marked the cap. The cap moved about 2" from ice expansion. This was a 48" tube, do 2" would be a 4.2% expansion. Ice can expand up to 10%. Ice can move with tremendous force in the right conditions, but most piping is never 90% full to begin with.
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