Pentair MasterTemp 125 - gushing water from manifold

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MattyC

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Jun 20, 2023
7
PA
Ok everybody. Here's the story. Pool heater is about 2 years old and always worked great. I'm usually the person who turns it off and on, but my wife decided to this time. Problem is she decided to close/open the valves that bypass the heater, but didn't do it correctly. So the water was able to flow into the heater, but the valve was closed on the exit side. I wasn't home, but she said there was a pop sound and then she shut overthing off.

When I came home and tested it out, it's gushing water from the bottom of the manifold. I took the manifold off to see if there were any noticeable damage to it or the o-rings. They all look clean/fine, as far as I can tell. I've seen a thread talk about the heat exchanger and if it protrudes .5" or not, and if the pipe ends look clean. Both are true, pipes clean, and they are poking out. The gaskets around the pipes appear fine too.

I also read a post talking about removing the bottom bolt to see if water comes from that, but if its already gushing out of the manifold - i imagine it would come out of there too. Does this sound like the heat exchanger is broke, or the manifold is shot, or something else I haven't read yet? Thanks for your help!
 
This is basically the same design heater as the Jandy. I suspect the water pressure cracked the manifold. It is held on by around 20 bolts. I think you are going to need to remove them. With any luck, it's just the manifold which you can replace.

You can also look in the ignitor hole (after removing it) and see if any water is inside the combustion chamber. It should be dry.
 
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ajw22 said:
And while you are repairing the heater change your bypass setup to a 3-way diverter on the input and a check valve on the output so the heater cannot be deadheaded as described in Heater Bypass - Further Reading
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Oh man - my bypass is exactly like this, except one important feature - that check valve. I just have a manual valve in that location - but now understand a check valve is the way to go, thanks!
 
MattyC said:
Oh man - my bypass is exactly like this, except one important feature - that check valve. I just have a manual valve in that location - but now understand a check valve is the way to go, thanks!
Click to expand...
Then you should be able to remove the 2-way diverter and screw in the check valve mechanism without any PVC surgery.
 
I did take it off and didn't really see a crack... maybe i just overlooked it. I'll buy a new manifold, but I just wanted to see if the consensus was, that's the most likely malfunctioning part.
 

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MattyC said:
I did take it off and didn't really see a crack... maybe i just overlooked it. I'll buy a new manifold, but I just wanted to see if the consensus was, that's the most likely malfunctioning part.
Click to expand...

It could be the manifold or it could be that part the manifold attaches to. Can't you put a camera under there and take a look?
 
PoolGate said:
I watched the video again it looks like the manifold. Possibly right at the seem so when it is not leaking it is hard to tell.
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PG - I took the manifold all the way out and inspected it closely and you are correct, there was a crack along the entire seem that was hard to see. I ordered a new one, so we'll see if that completely resolves the problem.

Thanks for everyone taking the time to respond and try to help out!
 
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