Main drain - temporary plug?


Silver Supporter
Mar 8, 2018
Seattle, WA
We bought a house two years ago with a 16k gallon pool. There was a SP1082GV main drain balancing butterfly valve since the main drain and skimmer are in series, but it was pretty old and broken and not screwed in place. The main drain port underneath had a plug inserted (pushed) in and I have been concerned to pull the plug out since the previous owner didn't know anything about it. There was a main drain cover at some point, as there are some broken remnants at the bottom of the pool. I dove down the other day and see that it is a 1 1/2" MPT threaded suction port.

If figured if there was a leak, that it would have been plugged on both ends. However, the drain outlet in the pool was not plugged...and I had the bright idea to get out my steel electrical fish tape and see how far back up the water goes into the main drain pipe. It goes all the way up to the skimmer it seems based on measuring out how many feet went into the pipe. So, that means it is also filled with water up to the main drain plug.

So my questions/thoughts are:

1. I presume the main was plugged/closed during some pool service LONG ago and left that way. The previous owners were not the familiar with their pool system, despite having had it put in. IF IT HAD BEEN FOR A LEAK, they would have plugged both ends and not allowed water into the drain pipe. Our pool water has been very consistent level for the last two years, except expected evaporation during really hot weeks. It seems like I should NOT be concerned with removing the plug and getting the main drain operating again. Thoughts?

2. I want to get a 1 1/2" MPT threaded main drain insert with VGB cover, but I am having trouble finding one for a pool. I can find ones for side drains on spas, like the Waterway 640-8240V 6" Ultra Suction Model 1.5" threaded VGB cover. Does anyone recommend a threaded 1.5" main drain VGB cover?



TFP Expert
LifeTime Supporter
May 3, 2007
Pleasanton, CA
Pool Size
Salt Water Generator


Silver Supporter
Mar 8, 2018
Seattle, WA
Thanks @mas985.

My fiberglass pool has no well, it just has a 1.5" threaded main drain line coming out of the bottom on the deep end. The only VGB cover I can find with a 1.5" threaded fitting is the Waterway 640-8240 V. Remnants of the cover that was used were in the bottom of the drain, and it matches the 1.5" drain cover from my inground spa.

For safety I'll put the Waterway cover on, in the event someone opens the main drain. While it would be nice to have the main drain open slightly, I may just leave it plugged.
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