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Thread: How do I seal damaged threads on 2" pump housing outlet?

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    How do I seal damaged threads on 2" pump housing outlet?

    After a long, drawn out fiasco with pool guys and pump motors, pump motor is replaced, up and running. Unfortunately, the pump housing was jostled when the pool guy installed the motor, and now I have a leak at the pump housing outlet. It seeps at at least one drip per second.

    It previously had some very soft black sealant of some sort covering the outside of the pipe where it met the pump. Don't know what it was, but it didn't leak - but it did indicate that they'd had trouble before.

    Disassembled and found that the threads are damaged on the pump housing, which appears to be black plastic of an unknown type. Looks like someone drug a screwdriver across the threads, and I'm betting that's why it's leaking.

    Tried teflon tape and it leaked. Tried silicone and it leaked. Tried pipe dope and it leaked. Tried windshield urethane (for installing windshield in a car - thought it had the right mix of rubbery-ness and strength, and it lasted about half a day before starting to leak. Assuming I can get the pipe to come out (windshield urethane is tough stuff, pipe is quite possibly glued in), does anyone have any suggestions for fixing this? I don't care if I have to glue it together permanently, as long as it stops leaking. I'd just solvent weld with purple primer and clear cement, but I didn't know if that'd work on the plastic the pump is made of.

    Also, how hard do I crank down? Using very large water pump pliers, 26" IIRC. Afraid of breaking the housing.
    25,000 gallon 18x36 vinyl inground, sand filter, been doing this a few years now and feel like I have a decent handle on it.

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    Richard320's Avatar
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    Re: How do I seal damaged threads on 2" pump housing outlet?

    Maybe it's time for some cyanoacrylic gel or epoxy.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
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    Mod Squad Bama Rambler's Avatar
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    Re: How do I seal damaged threads on 2" pump housing outlet?

    Some pumps have both internal and external threads. Is your's on of those?

    Assuming it's not, and you can get it apart and clean it well, and the threads are damaged badly then you might have to use some epoxy on it. I doubt solvent cements (PVC glue) will work. Be warned that if you go the epoxy route and it still leaks then the only option left is replacement.
    Dave J. TFP Moderator
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    stev32k's Avatar
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    Re: How do I seal damaged threads on 2" pump housing outlet?

    Are you sure it's the housing threads that are damaged and not the pipe threads? And is the housing cracked? If the housing threads are damaged you can usually re-cut them using a piece threaded steel pipe. Get a 2" black iron nipple and screw it into the housing about half to one thread at a time then back it out to remove any cuttings and repeat until you thread the entire length. Make sure the nipple goes in square so you don't cross-thread the fitting. At the same time use a 2" threaded steel coupling to clean the threads on the pipe. If your housing is not cracked this will normally allow you use pipe dope or thread tape and will stop the leak. One caution is do not use any oil or cutting fluid when threading or re-threading PVC. The oil can cause the fine cuttings to stick and prevent the threads from being cut and can cause the pipe to crack if you apply too much force (been there, done that).

    Edit: One thing I didn't point out is that you must be very careful to remove all cuttings from the steel pipe and the PVC after every turn. I use a tooth brush to clean both sides every time I back the nipple out. When you hit a bad spot on the PVC threads it will require some force to re-cut, but only cut about half the thread then back the nipple out and clean. Repeat until the nipple screws in and out smoothly with just finger tip pressure.
    20' x 40' IG with vinyl liner volume approx. 35,000 gal.1.5 H.P. main pump, Polaris 280 cleaner W/ 3/4 H.P. booster pump
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    Re: How do I seal damaged threads on 2" pump housing outlet?

    Welcome to TFP!!

    While those are nice answers, as well as being mechanically sound... do you want a less expensive 'possible fix'

    Try what I call the "triple threat" clean all the old teflon and pipe dope, etc. from both the male and female threads, then put a 1 1/2" o-ring on the male adapter. after it's snugged to the base of the threads, apply 4 wraps of Teflon tape to the visible threads and then smear Permatex, or similar on the top 3/4s of the threads. Screw the male adapter into the pump until the o-ring touches it and give it 1/4 turn more. You don't want to pinch the o-ring and cause it to 'pinch out' of contact with the pump housing!

    As long as the housing itself isn't cracked, this should seal the drip
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    Re: How do I seal damaged threads on 2" pump housing outlet?

    Thanks for all the ideas!
    Quote Originally Posted by Richard320
    Maybe it's time for some cyanoacrylic gel or epoxy.
    I guess I don't think cyanoacrylate will get it... and even epoxy makes me wonder; after all, it sets up hard and has no pliability to it. Afraid it'll set up but still seep. Any particular epoxy you've used to deal with this before?
    Quote Originally Posted by Bama Rambler
    Some pumps have both internal and external threads. Is your's on of those?

    Assuming it's not, and you can get it apart and clean it well, and the threads are damaged badly then you might have to use some epoxy on it. I doubt solvent cements (PVC glue) will work. Be warned that if you go the epoxy route and it still leaks then the only option left is replacement.
    No external threads, unfortunately. Yeah, being unable to disassemble it ever again is one of the reasons why I haven't used epoxy.
    Quote Originally Posted by stev32k
    Are you sure it's the housing threads that are damaged and not the pipe threads? And is the housing cracked? If the housing threads are damaged you can usually re-cut them using a piece threaded steel pipe. Get a 2" black iron nipple and screw it into the housing about half to one thread at a time then back it out to remove any cuttings and repeat until you thread the entire length. Make sure the nipple goes in square so you don't cross-thread the fitting. At the same time use a 2" threaded steel coupling to clean the threads on the pipe. If your housing is not cracked this will normally allow you use pipe dope or thread tape and will stop the leak. One caution is do not use any oil or cutting fluid when threading or re-threading PVC. The oil can cause the fine cuttings to stick and prevent the threads from being cut and can cause the pipe to crack if you apply too much force (been there, done that).

    Edit: One thing I didn't point out is that you must be very careful to remove all cuttings from the steel pipe and the PVC after every turn. I use a tooth brush to clean both sides every time I back the nipple out. When you hit a bad spot on the PVC threads it will require some force to re-cut, but only cut about half the thread then back the nipple out and clean. Repeat until the nipple screws in and out smoothly with just finger tip pressure.
    Yes, I replaced the pipe. It's the housing threads for sure. (And no, thank God the housing isn't cracked, at least not yet.) When I took the pipe out, I didn't notice any damage to the threads from being threaded into the housing... but I'll look closer. Buddy at work suggested the steel pipe idea (though he didn't go so far as using another steel coupling to clean threads!), but I didn't think there was enough plastic there in the housing to improve on the threads. I like the way this idea sounds.
    Quote Originally Posted by waste
    Welcome to TFP!!
    While those are nice answers, as well as being mechanically sound... do you want a less expensive 'possible fix'

    Try what I call the "triple threat" clean all the old teflon and pipe dope, etc. from both the male and female threads, then put a 1 1/2" o-ring on the male adapter. after it's snugged to the base of the threads, apply 4 wraps of Teflon tape to the visible threads and then smear Permatex, or similar on the top 3/4s of the threads. Screw the male adapter into the pump until the o-ring touches it and give it 1/4 turn more. You don't want to pinch the o-ring and cause it to 'pinch out' of contact with the pump housing!

    As long as the housing itself isn't cracked, this should seal the drip
    Thought of permatex but forgot about it. O-ring sounds like a good idea.

    It will be a while 'til I get to it, but I think when I get on this again, I will start by trying to re-thread with steel pipe and experiment with sealants. I might wait 'til the end of pool season, in case the housing breaks when I attempt to take out the urethaned-in pipe. Thanks so much for all the suggestions - when I do get to this, I will let you all know. Thanks again!
    25,000 gallon 18x36 vinyl inground, sand filter, been doing this a few years now and feel like I have a decent handle on it.

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    Re: How do I seal damaged threads on 2" pump housing outlet?

    I have used PVC glue to glue a fitting into a pump and it worked well. You only put the glue on the male threads to avoid getting glue dripped into the impeller. You have to allow at least 12 hours for the glue to dry before pressurizing it. Apply the glue and then hand thread the fitting into place as far as it will go by hand. Try to do it quickly without stopping. Don't use any tools, hand tight will be enough. I recommend using a schedule 80 cpvc nipple for best results.

    The damage to the threads is probably due to someone cutting the old fitting out with a hacksaw blade and going too deep. You can get out an old fitting by cutting through the inside of the fitting down to the threads on both sides and then prying the pieces out.

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    Swamp Thing's Avatar
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    Re: How do I seal damaged threads on 2" pump housing outlet?

    Quote Originally Posted by waste
    Try what I call the "triple threat"...
    This was awesome advice...I applied the "Triple Threat" yesterday after almost giving up on stopping a slow drip where the PVC exits the pump.

    I did change the application to the following:
    Great White dope on the male threads.
    2 wraps of Teflon tape over the dope.
    1 o-ring inside the threaded female pump housing.
    1 o-ring over the male threaded PVC pipe.

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    Re: How do I seal damaged threads on 2" pump housing outlet?

    blue monster tape works for me

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    Re: How do I seal damaged threads on 2" pump housing outlet?

    Quote Originally Posted by Swamp Thing
    Quote Originally Posted by waste
    Try what I call the "triple threat"...
    This was awesome advice...I applied the "Triple Threat" yesterday after almost giving up on stopping a slow drip where the PVC exits the pump.

    I did change the application to the following:
    Great White dope on the male threads.
    2 wraps of Teflon tape over the dope.
    1 o-ring inside the threaded female pump housing.
    1 o-ring over the male threaded PVC pipe.

    I follow what you did until the part about the o-ring inside the female pump housing. I just can't visualize what is keeping the internal ring in place. The male part is straigh-forward.
    21,000 gallon Diamond Brite Blue, Hayward Star Clear Plus 1200 Cartridge filter, Polaris 280, TF-100 Test Kit.

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    Swamp Thing's Avatar
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    Re: How do I seal damaged threads on 2" pump housing outlet?

    There was a small inner ledge for the o-ring to sit on.
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    Re: How do I seal damaged threads on 2" pump housing outlet?

    Thought I'd update to thank you all for your help, as well as to provide a resource in case anyone else has similar trouble. Permanently glued a 4" chunk of threaded steel male pipe into pump housing, then used a threaded female metal coupler with pipe dope to go to plastic pipe. To seal the steel pipe to the pump housing, I ended up using 3M Panel Bond (2-part epoxy we use in autobody shop to glue quarter panels and door skins on cars - it requires a special gun to dispense). I think JB weld would have been just as good.

    Tried to use O-ring I bought at Ace Hardware, but ran out of threads before it compressed... it turned out to be unnecessary though. Ace had a threaded collar about 1/4" thick I should've purchased and used to crank down on O-ring, though I still don't know if it would've sealed without being completely encapsulated.

    For anyone who needs to do anything like this, I read that when transitioning from threaded pvc pipe to threaded steel pipe, the pvc should be male or it won't seal well. Even following this rule, there is a super-slow seep (I'm thinking it measures a few drops per hour) where my threaded steel meets threaded pvc - if it gets worse I will try thick teflon tape or else Metal Bond or JB Weld. But it is 1,000 times better than the old leak.

    Forgot to take pics of finished product with plastic pipe attached, but here are the two metal pipes atop the world's ugliest pool pump. Shiny black ring is panel bond that's squeezed out; dull black ring is my O-ring that's not doing anything:







    25,000 gallon 18x36 vinyl inground, sand filter, been doing this a few years now and feel like I have a decent handle on it.

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    Mod Squad Bama Rambler's Avatar
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    Re: How do I seal damaged threads on 2" pump housing outlet?

    Good fix.
    Dave J. TFP Moderator
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    Re: How do I seal damaged threads on 2" pump housing outlet?

    I know this is an old thread.......But for any future pump discharge leak repair persons that might want to know a really good way to fix this problem, or one similar, here it is. The front housing can be found with little effort either locally or online part # PEN355468 for under $100. Then you use 2" CPVC (CPVC because it is heat resistant, and corrosion resistant because it is plastic) for the pump discharge. For the threads use "plasto joint stick" compound found readily at any reputable pool supply or online. The best part about doing it this way is that if any pool professional finds him/herself in your backyard, they are less likely to badmouth the handy work of "the last pool guy that did this repair", thus creating an awkward moment between the pool pro and the handy fellow responsible for the creative plumbing work.

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    Re: How do I seal damaged threads on 2" pump housing outlet?

    Quote Originally Posted by PoolDr2112
    I know this is an old thread.......But for any future pump discharge leak repair persons that might want to know a really good way to fix this problem, or one similar, here it is. The front housing can be found with little effort either locally or online part # PEN355468 for under $100. Then you use 2" CPVC (CPVC because it is heat resistant, and corrosion resistant because it is plastic) for the pump discharge. For the threads use "plasto joint stick" compound found readily at any reputable pool supply or online. The best part about doing it this way is that if any pool professional finds him/herself in your backyard, they are less likely to badmouth the handy work of "the last pool guy that did this repair", thus creating an awkward moment between the pool pro and the handy fellow responsible for the creative plumbing work.
    This handy fellow is broke as a joke and spent around $15, and is not easily offended by the pool pro he cannot afford. And I when I throw real money at this, it will be for a smaller pump and motor.

    But thanks for the pointer, should be helpful to someone.
    25,000 gallon 18x36 vinyl inground, sand filter, been doing this a few years now and feel like I have a decent handle on it.

  16. Back To Top    #16

    Re: How do I seal damaged threads on 2" pump housing outlet?

    This worked for me in the exact situation. There was a 1/16 in. gash across all the female threads. I cleaned the male and female threads as well as I could with paint thinner. Then I mixed a very small amount of white epoxy that is used for making small repairs to pool plaster according to the manufacturer's instructions, laid a very small bead of it into the gash with a little excess (only the gash area), wrapped the full flight of male threads with a single layer of Teflon tape and installed as usual. After 24 hours, I turned the pump on with no leakage. The hardened epoxy formed water-tight new threads but will not prevent removal of the pipe later.

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    Re: How do I seal damaged threads on 2" pump housing outlet?

    Quote Originally Posted by stev32k View Post
    Are you sure it's the housing threads that are damaged and not the pipe threads? And is the housing cracked? If the housing threads are damaged you can usually re-cut them using a piece threaded steel pipe. Get a 2" black iron nipple and screw it into the housing about half to one thread at a time then back it out to remove any cuttings and repeat until you thread the entire length. Make sure the nipple goes in square so you don't cross-thread the fitting. At the same time use a 2" threaded steel coupling to clean the threads on the pipe. If your housing is not cracked this will normally allow you use pipe dope or thread tape and will stop the leak. One caution is do not use any oil or cutting fluid when threading or re-threading PVC. The oil can cause the fine cuttings to stick and prevent the threads from being cut and can cause the pipe to crack if you apply too much force (been there, done that).

    Edit: One thing I didn't point out is that you must be very careful to remove all cuttings from the steel pipe and the PVC after every turn. I use a tooth brush to clean both sides every time I back the nipple out. When you hit a bad spot on the PVC threads it will require some force to re-cut, but only cut about half the thread then back the nipple out and clean. Repeat until the nipple screws in and out smoothly with just finger tip pressure.
    Not to bring back a dead thread, but will this work with something available at home depot?
    8000 gal diamond brite pool with 650 gal spillover spa, Pentair 3hp VS pump. Jandy Cartridge filter and Jandy Heat Pump. Jandy PDA automation system with 2 Pentair Laminars. SmartPool NC74S Robotic Pool Cleaner.

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