Suction side air leak only when vacuuming

[aeh0603]

So after ruling out some incorrect guesses, I now think I have a suction side air leak that is only noticeable when vacuuming.

Ever since we installed our new pump, the pump basket partially fills with air the second the vacuum hose is plugged in. At first I thought the problem was the hose because we accidentally bought and 1.25 in. diameter hose instead of a 1.5 in. diameter hose. I incorrectly assumed that since this pump is slightly stronger than our old once (1hp vs 3/4hp) that it just couldn't pull enough water through the smaller diameter hose on high speed. We recently bought a 1.5 in. diameter hose and there is no difference. It then occurred to me that there are people with much stronger pumps that are able to vacuum without issue so hose diameter is unrelated to my problem. Logically, if my basket not filling with water is not cause by a lack of water, then air must be getting pulled in from somewhere.

So far I've tried tightening the lid, which resulted in about 50% less air in the basket. I then removed the lid and added some extra pool lube to the seal. There was no real difference, but I only added the lube to the visible side of the o-ring.

• My next step is gong to be adding more lube to both sides of the pump lid o-ring.
• If that doesn't solve it I think the next step should be doing the same thing to the o-ring at the front of the pump

Am I on the right track? I chatted to the guy at the pool store about it when we were buying more liquid chlorine, but 1/2 of what they say makes no sense so I never trust their advice. For your reading amusement, they were convinced the problem had to be the hose or the vacuum because the problem only happens when the hose is plugged in despite the fact that I have tried 2 different brand new hoses and the rest of the vacuum assembly is under water. If the underwater part leaked, it would pull in water not air, and the likelihood of 2 brand new, different brand, different size pool hoses having the same leaking problem seems pretty small. Also, I'm using a manual vacuum head so it's not exactly possible for one of those to cause an air leak.

 

[mknauss]

Suction head increases when the vac hose is installed. So look st the suction side at the pump. Most likely is the lid gasket needing fully lubricated or replaced. Check the drain plugs on the pump as they have oring. The seal at the wet end I believe is on the pressure side.

 

[sktn77a]

We had the same issue in our pool since it was built 25 years ago (air in the pump basket when vacuuming). Our pool plumbing was pressure tested when we renovated, two years ago, and everything was A-OK. We still have air bubbles in the pump basket when we vacuum, so I'm guessing it's the lid gasket (even though it's clean, well lubed, and on tight).