Leak in main drain line with check valve?

[doncaruana]

Well, I think I have a leak in my main drain line somewhere. The shot below is my pump and the valve that switches between the main drain and the skimmer. Near the ground of both lines you'll see a check valve, one of them with the see-through window - that's the main drain line.

With the pump running, if I shut off the main drain line, you see nothing. If I shut the pump off, it stays good. However, as soon as I start opening that main drain line, you start seeing bubbles flowing through the see-through valve in a stead stream. You can hear almost a trickling down in the line as it goes underground as well. Below the check valve, the place I had close the pool last year drilled a plug so they could fill it with antifreeze or something. I checked it with shaving cream and didn't notice anything. I was able to tighten almost a half turn but it didn't seem to change anything.

So, my feeling all along has been that if the system was airtight like it's supposed to be, I shouldn't be getting air bubbles flowing through that check valve and water leaking. For that matter, I'm not quite understanding why, since this is a check valve, air is escaping up and water going down anyway (educate me please).

Anyway, to sum up, looks like there is a drain somewhere below the check valve, assuming the check valve is operating properly. Is that a rational conclusion? And how in God's name do I find it? Does it sound like I one of the lucky ones who got a below ground leak?

Thanks for any help you all can offer...

 

[jblizzle]

If you can see the bubbles coming up from below the check valve, then that certainly would point to a leak below it.

I am not sure what you question is about the check valve (educate me)? They are there just to prevent the water from draining back to the pool so the pump can prime easier.

 

[doncaruana]

The educate me part is because I'm not quite understanding why the water is draining back into the pool if there is a check valve there, air bubbles notwithstanding. When I start this up after it's down for a bit, the pump has to work pretty hard to pull prime (3400rpm for about 3-4 minutes after sitting overnight.

One thing I've been thinking about my issue. My pump (and these lines) is above the pool. In 3 days, I've had about a half inch of water drop despite back-to-back 80+ degree sunny days. I'm kind of thinking that should mean that it's not too likely that the air leak is very far down the line because I don't have a water leak to speak of. Does that make sense? I had it explained to me previously here that rushing water sometimes doesn't find holes that air will.

I wish they hadn't jammed everything right up next to the other line or the ground - makes it extremely difficult to get to.

 

[doncaruana]

You know, thinking about this some more, I'm even more confused...

If I have the valve to the main drain line closed, the water in that line stays static and I don't have air bubbles free flowing, etc. As soon as I open it for the main drain (this is at the top of the two lines), here come the bubbles and the water starts dropping. All I have is speculation as to how this happens or what it means...

 

[jblizzle]

Inspect the check valve and see if it is not sealing ... that would let the water drain, but would not explain the suction air leak. Seems like 2 possible problems with that line.

 

[doncaruana]

Seems like 2 possible problems with that line.

That's what I've had swirling in my head. Because, of course, it's never simple.

How do I check exactly if it's not sealing though? Is that something I should be able to see with the naked eye? Not sure what exactly I'm looking for.

 

[jblizzle]

Take the front off the check valve and see if the rubber look ok. I have never done it so also not sure what to look for

 

[doncaruana]

Opened the check valve, seemed fine. However, tried shaving cream and water on the plug right below the check valve. Shaving cream was slow, but after a while it looked like a hole was appearing. Water test was much better. No water, bubbles galore in the check valve. Water on the plug, bubbles almost disappeared. So, there still may be more leaks, but there's at least one here. It seems like it's not the plug itself but the collar they put in for the plug to go in to.