losing suction with vacuum hose - can't solve this mystery

[KNIGHTCAP]

I can't figure this out, and am hoping someone can help. I have a 30,000 gallon, inground pool, 2 skimmers, one main drain. When I vacuum, I attach the hose to a plate, put the plate in one skimmer, then shut off the other skimmer and main drain (or almost shut off, just a trickle).

I've done it this way for years. Now, when I turn off the other skimmer and main drain, within seconds my pump loses all prime, the lint pot fills with air. Its almost like the end of the hose is out of the water, and not attached to the vacuum head. I've checked it repeatedly. The vacuum head is under water, at the bottom of the pool.

If I close a skimmer and main drain, and leave one skimmer open, with no vacuum or hose hooked up, it works fine.

I thought maybe my hose was blocked or had a leak, so I borrowed my neighbor's hose and skimmer plate, and have the same problem. I've tried it in both skimmers, same problem.

Somehow, the skimmer is drawing in air with the hose attached. I can hear a little air hissing where the hose enters the cuff ( the piece that attached to the skimmer plate), but I've always heard that. I usually wiggle the host a bit until its minimal. My neighbor's hose has the same hissing sound.

Help me please, if you can.

 

[duraleigh]

Suction side air leaks are very hard to find but usually easy to fix. If you eliminate ALL the vacuum apparatus, do you still suck air?

 

[KNIGHTCAP]

no, no leaks with vacuum disconnected. I try closing main drain and one skimmer, so only draw from one skimmer, and no leaks. Did this with both skimmers, and with the main drain, both skimmers closed. So each of the three can draw, with no leaks. (A few bubbles from on skimmer, but I think this is called cavitation, not getting enough water).

 

[Richard320]

Don't be insulted, but I have to ask.... you are filling the hose with water before connecting it, aren't you? I like to set the head in and then feed the hose down vertically so it pushes air out. When it's full, I shove it through the skimmer throat and plug in.

 

[KNIGHTCAP]

not insulted! Yes, I always fill the hose with water. I think I'm doing it your way - attach to the head, push that to the bottom of the deep end, then feed the hose in vertically, then keep the other end in the water. I think I learned that trick from this site!

 

[Richard320]

It sure sounds like maybe both hoses have leaks, since there's no air leak without them.

Is there any way to get some extra hands on it and hold the whole hose below the surface? If it doesn't lose prime, you've solved the mystery. You might even see a vortex where it's sucking water in through the crack.

 

[KNIGHTCAP]

I could try something like that, but way too cold now to get in the pool. But my neighbor just vacuumed his pool, and had no issues, that's why I borrowed his hose. If his worked, I was going to buy a new hose. But now, I'm not sure, unless his hose has a leak that wasn't apparent to him?