How "watertight" and "airtight" are properly installed PVC ball valves?

[bobdobalina]

How "watertight" and "airtight" are properly installed PVC ball valves?

I have what I think is a suction-side leak on my fountain circuit. Since we have owned the house, the pump would never self-prime (maybe that's to be expected as the pump sits 6-8 feet above the water level), but now it seems the basket empties of water after just a few hours of downtime.

One way I can narrow down the problem would be to close the ball valve (for a few days, I'd guess) that's on the return side and see if the water falls, but I need to know whether this makes sense as a test. If I close the valve, should any air be able to get in the line?

Thanks.

 

[Bama Rambler]

Re: How "watertight" and "airtight" are properly installed PVC ball valves?

While those valves can leak around the stem (any valve can really), it's really rare to have that happen. Especially when it's closed. In order for it to leak around the stem when it's closed it would have to leak by the ball seal and then also leak by the stem seal.