High Tide Aquatics

Threaded PVC fittings leaking

porksmash

porksmash

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I'm setting up my new tank and decided to use threaded bulkheads for convenience. My problem is my standpipes leak through the threads between the MPT adapter and the bulkhead. The bulkhead seal against the glass and the pipe inside the thread adapter are both solidly sealed.

I'm using this bulkhead and this MPT adapter. I've tried teflon tape, no teflon tape, various amounts of tightness from loose as a goose to needing two wrenches and a manly grunt to get it back apart and it still leaks. It leaks pretty good too at about a couple drops per second. That's only with the overflow box about half full.

Would putting a smear of silicone on the threads be ok? LASCO says don't use teflon tape, but do use a sealant. Silicone is a reef safe sealant I have already but I don't know how well it would work over time given that it's attachment to plastic isn't that great. BRS reviews on the bulkhead mention teflon tape mostly.
 
Been silicone sealing my threads for 20 years and works like a charm. Usually use a little Teflon tape as well to help stiffen the connection.
 
Check the threads on both the bulkhead and the fitting. Make sure they are not worn out. If Teflon tape is not working, I'd change the bulkhead and fitting.
 
If Teflon tape, be sure to wrap it in the right direction (ie, twisting on isn't counter wrap direction). This is one of the big reasons vacuum NPT fittings leak (in my field).
 
The MPT adapter does have a taper and the threads are in good condition. BRS recommended using 4-5 wraps of teflon tape which is more than I was using, but I think I like silicone better. Thanks for the comments!
 
Gomer said:
If Teflon tape, be sure to wrap it in the right direction (ie, twisting on isn't counter wrap direction). This is one of the big reasons vacuum NPT fittings leak (in my field).
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I thought it was because some post doc reassembles compression fittings with NPT pieces :D
 
anderson99 said:
What type of silicone does everyone use? I have one MPT fitting with some salt creep. I'd like to make sure it is completely sealed.
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I just applied some GE Silicone I that I had laying around from the last time I messed with my sump baffles. Waiting until tomorrow for it to cure and then test time!
 
I'm living on the edge; only let it cure for 22.5 hours. So far so good, totally leak proof. I'm very pleased after the hours of tightening and redoing the plumbing yesterday. I still need to test with the tank completely full and the ball valves on my drains closed to see if it can stand the maximum pressure it'll ever experience, though. I have high hopes.
 
Risky behavior like that does not set the best example for our young reefers.
Young rookie,newbies please,please let the silicone cure and be sure to QT all your livestock too!!!!
 
At the store we use "pipe dope" on all the threaded connections. It is way more fool proof than teflon tape BUT it can get messy, I mean real messy. They have different ones out there but use one that is OK for potable water and you should be fine.
 
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