Frozen backwash pipe

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JJ_Tex

JJ_Tex

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Jul 17, 2019
3,790
Prosper, TX (DFW)
Pool Size
13000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
I just went outside to check on everything and found that my backwash line from the multiport valve to the sewer line is frozen solid.

During snowmageddon a few years ago it froze as well and I replaced it. When I replaced the PVC I added a screw top so I could take a peek and see if there is ever water in it. I kept an eye on it for a few months and it was always dry as a bone. I was curious/bored a second ago and screwed off the top and can see it is frozen solid. I added some heat tape, but guessing the PVC will have to be replaced before I backwash again.

I'm 75% sure that means I have some sort of leak in my multiport, but I wanted to be sure. Anyone have any thoughts?

IMG_9187.jpg


IMG_9186.jpg
 
Where does it go ? To the sewer or the yard ?

MPV leak or no leak, It will only be full of pool water if there is a blockage downstream (IIRC you corrected the pitch with the previous repair).
 
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Newdude said:
Where does it go ? To the sewer or the yard ?

MPV leak or no leak, It will only be full of pool water if there is a blockage downstream (IIRC you corrected the pitch with the previous repair).
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It goes underground to the front yard then pops up and goes into the sewer line. By code there is an air gap between the backwash and sewer, so I can see lots of water coming through when I actually backwash.
 
JJ_Tex said:
By code there is an air gap between the backwash and sewer, so I can see lots of water coming through when I actually backwash.
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Ok so you have a clog between the air gap and filter and also a leak. If it was just a leak it would drain forever. The clog caused backed up water which froze.
 
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Ok I've been thinking on it. This may become a yearly thing without some re-engineering. Sorry that we didn't know last year but the uphill pipe that was above ground was an open and shut case for trapped water. We couldn't have known there was another issue, but I think I got it.

The air gap is below the level of the above ground backwash pipe in order to drain. This isn't to scale but you get the idea.

Screenshot_20240114_183303_Chrome.jpg

In this scenario pipe 2 stays full of water at all times and if it's close to the surface, will freeze. The stoppage allows the leak (its own issue) to fill the aboveground pipe 1, which also freezes. Last year it cracked and it may this year also before it thaws.

Pipe 2 needs to be blown for the winter or this will continue to happen IMO. If it happens enough times, pipe 2 will eventually shatter and cause a MESS at the first backwash after that.
 
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Newdude said:
Ok I've been thinking on it. This may become a yearly thing without some re-engineering. Sorry that we didn't know last year but the uphill pipe that was above ground was an open and shut case for trapped water. We couldn't have known there was another issue, but I think I got it.

The air gap is below the level of the above ground backwash pipe in order to drain. This isn't to scale but you get the idea.

View attachment 549893

In this scenario pipe 2 stays full of water at all times and if it's close to the surface, will freeze. The stoppage allows the leak (its own issue) to fill the aboveground pipe 1, which also freezes. Last year it cracked and it may this year also before it thaws.

Pipe 2 needs to be blown for the winter or this will continue to happen IMO. If it happens enough times, pipe 2 will eventually shatter and cause a MESS at the first backwash after that.
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Thanks man. My plan this spring is to snake the pipe, repair any damage, the. Figure out what I need to do for the MPV to fix that leak.
 
You could install a tee with a threaded plug right after the discharge and use that to blow out only that line. We've done this will large threads and adapted to the exhaust on a shop vac, and it works well for us.

Edit* just realized I looked at the pictures but didn't look. You literally have exactly that. Carry on. :salut:
 
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JJ_Tex said:
Thanks man. My plan this spring is to snake the pipe, repair any damage, the. Figure out what I need to do for the MPV to fix that leak.
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The fittings used for plumbing like that don't play well with plumbing "snakes." There are hard 90s instead of sweep 90's that drains use. Get a snake past two and you may not get it back. First picture is a sweep, the second is what is usually installed.
1705344894832.png1705344970683.png
 
Another good reason to get rid of the DE filter - no backwash lines to worry about.

I use a simple push-pull plunger style backwash valve on my pool and, every couple of years, I’ll notice water building up in the backwash port (it’s not hard plumbed so I can see when there’s a leak). That’s my cue to get out my gasket set and rebuild the plunger valve. Not a big deal, but just one more thing to spring a leak. I’m probably just a year or so away from needing to update the equipment pad as all the equipment is past the 10 year mark. I may bite the bullet and simply tear everything out and redo it completely rather than replace one-off failures. One of these days there will the “Help me spec my new pad” threads …
 

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How far away is the sewer line ?

I don't think snaking is going to matter. The underground backwash pipe, or the top inch of it where is goes in the ground is frozen, not clogged.
 
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