Can't isolate skimmers from main drain

brajgreg

Well-known member
Apr 28, 2012
78
Houston, TX
Moved from here.
Under one of those skimmers there should be a second hole that leads to the main drain.

Beneath the skimmer basket there should be a diverter valve

or


Here's how the spaceship one works.

I found this when searching for a similar issue. I just bought a house with a pool, and the CYA is high so I'm trying to drain/refill. I thought I had shut off the skimmers, and was pumping my water to waste, but then I heard the pump sucking air. Sure enough, after re-filling above the skimmers to verify, my diverter valve switches from one skimmer to the other, but doesn't isolate skimmers from the main drain.

One of them does appear to have two holes, but if there's a valve under it? (in my inground pool), is there a way to close it off?

Thanks!
 
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mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
33,301
Laughlin, NV
If the skimmers are tied together, then there is a valve for just the main drain (or a three way valve with skimmers, main drain, and suction to pump all in one) at your equipment pad.

You should consider getting a sump pump to drain water from your pool. Using a pool pump for that purpose is not advised.

Are you working on a pool or the spa described in your signature?
 

brajgreg

Well-known member
Apr 28, 2012
78
Houston, TX
If the skimmers are tied together, then there is a valve for just the main drain (or a three way valve with skimmers, main drain, and suction to pump all in one) at your equipment pad.

You should consider getting a sump pump to drain water from your pool. Using a pool pump for that purpose is not advised.

Are you working on a pool or the spa described in your signature?
There is one valve on the line coming into the pump, and it appears to only switch between the shallow skimmer and the deep end skimmer. My assumption (I'll dive in the deep end in a bit to verify) is that on both settings, the main drains are sucking, but I'm not sure. There is no way for me to turn off both skimmers currently.

My signature was old. I don't have all of the details right now, but it's an inground gunite pool, approximately 18k gallons.

Edit: I wasn't aware you shouldn't use the pump to drain the pool. Why is that?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
33,301
Laughlin, NV
If you lose prime on the pool pump, you can damage or destroy it. Using an $80 sump pump is much safer.

If the main drain does not have a line running back to the equipment pad, it is plumbed into a skimmer. Or it is abandoned and does not pull any water at all.
 

brajgreg

Well-known member
Apr 28, 2012
78
Houston, TX
If you lose prime on the pool pump, you can damage or destroy it. Using an $80 sump pump is much safer.

If the main drain does not have a line running back to the equipment pad, it is plumbed into a skimmer. Or it is abandoned and does not pull any water at all.
Ok, so I have two open holes in one skimmer. This is my third pool but probably 6th or 7th that I've helped maintain, and I've never seen this setup. But this is also probably the oldest pool I've dealt with.

I'm really not sure what that second hole is supposed to accomplish. If I'm right in assuming that the second hole that doesn't suck is running down to the two main drains, is it supposed to somehow be pulling water through them? that won't work... This is confusing for me.

Every pool I've ever drained in the past had a dedicated line that I could switch to the main drain, and a waste setting on the multiport valve so I just did it that way without problem in the past. Looks like I might be getting a sump. Do you recommend renting one or buying one? Harbour Freight Special?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
33,301
Laughlin, NV
Do you have one skimmer or two?

A Harbor freight 1/2 hp is great for draining small amounts or doing a water exchange. To drain a large volume quickly, renting one at Home Depot or other is easier.
 

brajgreg

Well-known member
Apr 28, 2012
78
Houston, TX
Do you have one skimmer or two?

A Harbor freight 1/2 hp is great for draining small amounts or doing a water exchange. To drain a large volume quickly, renting one at Home Depot or other is easier.
Two skimmers, two main drains. The one in the deep end near the two main drains has the two holes open in it. the other one has a plugged hole and one open.
 

Rancho Cost-a-Lotta

Silver Supporter
Apr 10, 2018
1,620
Rancho Cucamonga, CA
The skimmer with two holes is likely plumbed to the main drain. If you want to pull water from the main drain, you need a float/diverter valve in the skimmer. Opening and closing the flap adjusts suction from the two sources (skimmer and drain). Since the valve is not air-tight, you can't use the pool pump to drain the pool. Your pump will start cavitating when the water gets below skimmer level...

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mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
33,301
Laughlin, NV
OK -- so the main drain is tied to the skimmer with two holes. To pull just from the main drain, you would need to set the valve to pull from the skimmer that has the two holes open, and use the diverter that should be over the two holes in the skimmer to divert to pulling from the main drain. If you do not have the diverter, then you need to get one. Or just let it be and get a sump pump.
 

brajgreg

Well-known member
Apr 28, 2012
78
Houston, TX
OK -- so the main drain is tied to the skimmer with two holes. To pull just from the main drain, you would need to set the valve to pull from the skimmer that has the two holes open, and use the diverter that should be over the two holes in the skimmer to divert to pulling from the main drain. If you do not have the diverter, then you need to get one. Or just let it be and get a sump pump.
Yeah, no diverter. Just two open holes. I'll go the sump route.

Does anyone have any insight into why a pool builder would go this route? assuming it was the original installer who did this. I can't think of a good reason for it, but maybe back in the day people had a reason?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
33,301
Laughlin, NV
It is cheaper. Our main drain is tied to our one skimmer. The diverter in ours works OK, but to be honest, there is no need for a main drain to begin with so I wish I had just told them to not install them. I set our diverter to full skimmer. I suspect the main drain pulls a little water, but who knows.