huge blast of air when pump starts

[poolgal13]

This morning I happened to be outside when the pump started and a HUGE amount of air came out of one of the pool jets. It was like a giant "blurp" and then smaller bubbles continued for about a minute. I know I must have air in the system, but where should I start looking? The pump strainer basket has no bubbles other than the one that always forms at the very top of the lid. So I don't think it's the O ring. Suggestions?

[mas985]

First, do you have solar? A VRV will allow air into the plumbing so every time you turn on the pump, you will get a burp of air. This is normal.

Second, when the pump is running, do you see any air in the pump basket? If so, then you do have a leak on the suction side of the pump. It could be the pump basket or pump drain plugs or a valve.

Third, on rare occasions, a filter can allow air into the filter while the pump is off. Once turned on, the air gets purged and then there is no more air after that. It doesn't always leak water out with the pump running so it isn't always very obvious. But this type of leak usually occurs in a backwash valve.

[poolgal13]

It did it again this morning--and I see no air in the pump basket, just water. I don't have solar heating.

I have a DE filter but I'm not sure where air would be entering? Is there anything else that might be easy to see?

Something that does worry me--when I opened the pool a few weeks ago, I was vacuuming up leaves. I made a big clog in the pipe right before the pump/pump basket which was stopping most of the water getting to the pump. I didn't realize this at first. Eventually we unclogged it but we had to re-prime the pump. My pool handbook says running the pump without water can ruin the "pump seal". What is the "pump seal" and would a ruined one let air into the system?

Otherwise I have no clue where to find it and it looks like I might need to call a pool person and spend big $$$.

[mas985]

No the pump seal is on the pressure side of the pump so when it leaks, it leaks out water.

A few more things to check.

When you run the pump for a while, does air start to accumulate in the filter? You can check by using the small valve at the top of the filter that bleeds out air when the pump is running.

When you shut off the pump, can you hear air bubbles rising in the filter? If so, this could mean the multi-port/backwash valve is leaking.

What is the brand and model number for your filter?

[poolgal13]

We have a Pentair DE filter, FNSP 48. I looked and there is a steady drip coming from a black plastic knob at the bottom of the filter. There also MAY be a drip from the "Inlet" part of the filter where a black connector on the filter joins up with my white PVC piping. Seems to be a small wet area where they connect.

[poolgal13]

I looked at a diagram and I think the black knob is the drain. So maybe it's the O-ring in the drain?

[mas985]

Some of those leaks could be leaking air into the filter while the pump is off. And yes, there is an o-ring in the drain fitting.


There also MAY be a drip from the "Inlet" part of the filter where a black connector on the filter joins up with my white PVC piping. Seems to be a small wet area where they connect.That sounds like the multi-port or push-pull valve and is a common place for some leaks. They too have gaskets/o-rings that can be replaced.

[poolgal13]

Thank you so much for helping. I guess our next step is to sort through some diagrams and figure out if we can do this ourselves or if we need to call the pool company.