Closing main drain / plumbing design

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Machinyo

Member
Oct 2, 2022
5
Toronto, Ontario, Canada
Hello and thanks in advance for your help.

I'm located in Toronto, Canada. I moved into a house last year with a pool. This year I plan to close it myself and I'm confident on everything except for blowing out the main drain.
  • In my equipment room there is 1 intake, I presume this means the main drain goes to the skimmer first and then the pump
  • At the bottom of my skimmer there are 2 holes, when I opened the pool, one had a rubber stopper and was easily removed. The other hole had a threaded plug and I was not able to remove it, so I assumed it was intended to be permanently closed
My questions are:
  1. How can I know for sure that the 2nd hole should be permanently closed?
  2. Related to that question, is how can I know how the lines are designed (image below of the options I think are possible)
  3. Does the main drain need to be blown out and air locked? This video suggests it does not need to be blown out, but I'm nervous about that and would like confirmation (I'm fairly certain it was not air locked by the folks that closed it last year).

    Screen Shot 2022-10-02 at 2.38.20 PM.png
 
Welcome to TFP! :wave: By chance, have you ever gone down to the main drain and removed the cover to check and see if it was plugged at the bottom? It's possible the main drain line leaked at some point in the past so it was plugged in the skimmer port. If so, then I would think it should also be plugged in the drain port. It's also possible the drain was never connected from the floor to the skimmer and it was always plugged in the skimmer port.
 
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M,

If you have two holes in the bottom of your skimmer and only one pipe coming into the pump, then the hole closest to the water is going to the main drain and the other hole is connected to your pump.

Main drains are not really needed, and many pools have no operating main drain, and they work just fine.

Thanks,

Jim R.
 
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Texas Splash said:
Welcome to TFP! :wave: By chance, have you ever gone down to the main drain and removed the cover to check and see if it was plugged at the bottom? It's possible the main drain line leaked at some point in the past so it was plugged in the skimmer port. If so, then I would think it should also be plugged in the drain port. It's also possible the drain was never connected from the floor to the skimmer and it was always plugged in the skimmer port.
Click to expand...
Thanks for the welcome and for the advice. I haven't tried this. Given the pool temp is now quite cold are there other options?

I assume this is a bad idea: drop the water level below the skimmer, plug the hole in the skimmer, then run the pump for a minute or two to see if it draws water from the main drain?
 
Machinyo said:
I assume this is a bad idea: drop the water level below the skimmer, plug the hole in the skimmer, then run the pump for a minute or two to see if it draws water from the main drain?
Click to expand...
That wouldn't work because:
1 - Either the drain below is already plugged or ..
2 - Once you lower the water level below the skimmer, it can't pull water from that 2nd hole (if open) anyways.

I would just leave it alone until next year. If in 2023 you are feeling adventurous, once you raise the water level back up, you can try to open that sealed plug, and/or wait until the water is warm enough to inspect the drain.
 
I have 2 skimmers and they both have 1 permanently closed hole, the other hole in each skimmer is able to be plugged.
When I blow my lines, I hook up my compressor to the pump through the drain screw at the basket area, turn on the compressor and air start to enter the pump and lines, as it fills the lines and pushes out the water , the first skimmer that clears , I plug it.
Then the second skimmer will clear and I plug it, then the water is pushed towards the main drain. When that bubbles, I turn the main drain valve to the off position and the same time shut off the compressor. That creates a air lock at the drain. I don’t build up pressure in the compressor, I just hook it up and turn it on. The ability of the compressor motor to fill the pipes and push out the water is sufficient. You won’t get 100% of the water out like with a high volume cyclone blower but you get out a majority. Any left over will end up in the main drain pipe which is below frost line and will not freeze anyway.
 
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Texas Splash said:
That wouldn't work because:
1 - Either the drain below is already plugged or ..
2 - Once you lower the water level below the skimmer, it can't pull water from that 2nd hole (if open) anyways.

I would just leave it alone until next year. If in 2023 you are feeling adventurous, once you raise the water level back up, you can try to open that sealed plug, and/or wait until the water is warm enough to inspect the drain.
Click to expand...
Thanks! So just to confirm... if it is not plugged below there's no/minimal risk of a pipe bursting? I'll drain the pool to below the returns, which is about 22" below ground.
 
Spitdog said:
I have 2 skimmers and they both have 1 permanently closed hole, the other hole in each skimmer is able to be plugged.
When I blow my lines, I hook up my compressor to the pump through the drain screw at the basket area, turn on the compressor and air start to enter the pump and lines, as it fills the lines and pushes out the water , the first skimmer that clears , I plug it.
Then the second skimmer will clear and I plug it, then the water is pushed towards the main drain. When that bubbles, I turn the main drain valve to the off position and the same time shut off the compressor. That creates a air lock at the drain. I don’t build up pressure in the compressor, I just hook it up and turn it on. The ability of the compressor motor to fill the pipes and push out the water is sufficient. You won’t get 100% of the water out like with a high volume cyclone blower but you get out a majority. Any left over will end up in the main drain pipe which is below frost line and will not freeze anyway.
Click to expand...
Thank you. I was thinking of this approach as well. Kept the compressor around 8 PSI?
 

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Machinyo said:
Thank you. I was thinking of this approach as well. Kept the compressor around 8 PSI?
Click to expand...
If you hook up the compressor hose like I stated above, your compressor will not build pressure Into the storage tank because the air is constantly being pumped into your pool lines. Thus no setting pressure manually.

Now if you removEd the hose from the nipple at the pump basket, then yes your compressor would start holding air in its tank and the pressure would build.
 
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Machinyo said:
Yes, it has a raised square. I tried my hand then a basin wrench.
Click to expand...
I have had to use a socket many times to get a good turn to loosen. I do not think it would be glued in. Be sure the water level is below skimmer mouth so if you do get it out water will not get just in case it was blown out and the other end is also plugged as another had suggested. Thing is IF the other end is not plugged that line can be full of water right up to the bottom of that plug and our frost will go lower than the bottom of the skimmer body.
 
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