Replacing Main Drain Ball Valve

[Juvenall]

My 10,000 gallon above ground has had a leaky main drain ball valve for the last two seasons, but I think I may need to replace it finally. Over the last few days, the pump has been losing prime and as best as I can tell, this is the most obvious culprit where air could be getting in.

How tricky of a repair would this be for someone with no plumbing experience? Since there's no way to close the main valve itself, is this sort of repair possible (by me or a professional) without draining the pool?

Here's a shot of valve in question

 

[Bama Rambler]

It's really not as hard as you might think.
First, where is it leaking from? If it's the union collar, just try tightening it up a bit.

If it's not that or it won't tighten, take a piece of plastic wrap and a piece of rubber (i.e. bath mat, exercise mat, etc.) and place the plastic wrap over the main drain and place the rubber mat over that. Weigh them down if you need to with a sand or salt bag. That will seal off the main drain. Plug the skimmer and you're all sealed off and ready to replace the valve. You're very lucky in that it's a threaded valve AND has a union collar. Just take the collar off and then you can unscrew the halves from the piping. Buy a tru union threaded valve to replace it with and you cna just screw it back into place.

 

[jblizzle]

and you can just screw it back into place.

... using teflon tape and/or non-hardening pipe dope.

 

[JohnT]

Over the last few days, the pump has been losing prime and as best as I can tell, this is the most obvious culprit where air could be getting in.

Unless your pump is elevated, you can't really lose prime on an AG pool without a restriction in your plumbing. Any chance your skimmer weir is sticking?


Sealing the drain enough to work on the valve is fairly easy, especially if somebody can get in the pool to help. I used an inverted rubber animal feed pan in my IG. If you want it bone dry, cram the cut end of the pipe with bread until it stops leaking, dry it off and then quickly put the closed valve on. Wait a few minutes and then open the valve and the bread will have dissolved enough to flush out through the valve. Then close the valve and finish plumbing.