Trying to understand blowing out the main drain...

[mjc123]

Hey all,

I've been following most of the closing threads, including Catanzaro's excellent thread (should be stickied, perhaps?), however, I am still not completely clear on the concept of blowing out the main drain line.

So the returns make sense - you lower the water level below the returns, and blow all the water out of the piping and plug the ends - what's left *should* just be air all winter. However, the main drain remains completely submerged. Surely even if you can build enough air pressure to blow it out and plug it, the water will just leak back in, because there's no way to plug the drain at the bottom. Am I missing something?

 

[Catanzaro]

Surely even if you can build enough air pressure to blow it out and plug it, the water will just leak back in, because there's no way to plug the drain at the bottom. Am I missing something?

Yes, you will need to close the shut off valve to the MD after it bubbles for 45 seconds to 90 seconds. You want to bring the water in the piping below the frost level. If you do not have a shut off valve, then purchase the black winter plugs with the Schrader valves that are part of my thread. The air is suspended in the piping. This is what they call an "air lock". Thanks!

 

[Marty D]

I didn’t understand it also but after you done all the pipes, and plug them do it again and air will come out of main drain, then close the valve that says-MD. That’s called air lock.

 

[mjc123]

Yes, you will need to close the shut off valve to the MD after it bubbles for 45 seconds to 90 seconds. You want to bring the water in the piping below the frost level. If you do not have a shut off valve, then purchase the black winter plugs with the Schrader valves that are part of my thread. The air is suspended in the piping. This is what they call an "air lock". Thanks!

Ah ok, I see what you mean now - just maintaining positive pressure in the pump end of the pipe to "hold" the water level down. I'm surprised that even with those rubber stoppers that it would maintain enough of a seal over the entire winter, but I suppose it's possible. In my case, I'm not sure how I could do that though. My MD hose meets up with the skimmer hose in a 3-way valve (Jandy valve?) that then goes into the input of the pump. I have no way to isolate and plug only the MD line without uncoupling the valve

 

[Catanzaro]

My MD hose meets up with the skimmer hose in a 3-way valve (Jandy valve?) that then goes into the input of the pump. I have no way to isolate and plug only the MD line without uncoupling the valve

Please upload a picture of the 3-way valve (Jandy Valve). If I am understanding correctly, you have a shut off valve, either for the skimmer or MD. Shut off the main drain first, then clear the skimmers completely. Then close off the skimmer(s) with a Gizzmo or black regular winter plug and place foam in the skimmer housing. Then turn the valve towards the MD and blow out the main drain the same way using the shut off valve. You can also leave the winter blow out plug in the plump basket of the pump (The one with the Schrader valve). Once the skimmer(s) are closed, the air will stop and travel the other way, but I believe your shut off valve will do the trick.

My system has 2 valves. One is for the MD (on or off). The other is a 3 way valve that control the 2 skimmers. With the locking pins, I can not close all 3, only 2 of them, therefore giving me the ability to work independently.

 

[mjc123]

Please upload a picture of the 3-way valve (Jandy Valve). If I am understanding correctly, you have a shut off valve, either for the skimmer or MD. Shut off the main drain first, then clear the skimmers completely. Then close off the skimmer(s) with a Gizzmo or black regular winter plug and place foam in the skimmer housing. Then turn the valve towards the MD and blow out the main drain the same way using the shut off valve. You can also leave the winter blow out plug in the plump basket of the pump (The one with the Schrader valve). Once the skimmer(s) are closed, the air will stop and travel the other way, but I believe your shut off valve will do the trick.

Here's a photo: https://u.cubeupload.com/mjc123/IMG3212.jpg

There appears to be a disconnect between the valve and the pump input, so I can either blow out from there or from the pump basket - I think. In any case, yes, I would first open the valve to the skimmer side and blow that out, then open it to the main drain side and blow that out. What I'm not sure of is whether that valve is airtight enough to maintain positive pressure in the pipe or if I'd need to plug it with something else

 

[Catanzaro]

Close the main drain and clear out the skimmer first. Then close the skimmer and clear the main drain. After the main drain bubbles a while, then close off the main drain (do not worry about the skimmer) and this will create the "air lock". You can quickly go in the pump basket and place a black plug as extra insurance. Or you can use the blow out plug with a compressor and move water with air this way.

If you lower the water below the skimmer, then use a shop vac to suck water out at the same time.