Bulkhead Thread Fitting, how do you prevent leaks?

[Bengalcats888]

Hi,

I making a 14 gallon filter using 1” and 2” bulkhead fittings.

I used silicon on both inside and outside when mounting to the barrel since due to the curvature of the barrel, it is not a flush fit. I did a leak test after 48 hours and no leaks.

I used threaded plugs on the bulkheads to check for leaks. I found I did not use enough teflon not tighten it enough and there small leaks at the thread joints.

I’m using standard PVC 40 fittings. Male NPT thread to slip.

My questions

1.How do you know when it is over tightened?
Are you supposed to tighten until all threads are in the bulkhead fitting?

2.Can I add silicon sealant on top of the teflon tape and then screw it on?

This barrel will be used indoors so needs to be leak proof.

 

[esoxlucius]

When tightening bulkheads you need to firstly have the gaskets in the right place and then tighten them as far as you can with your hand. Then just to be sure, a further quarter to half turn with a spanner/wrench. Do not over tighten bulkheads, they are only plastic and, although typically made of PVC or ABS, very tough plastics, over tightening can lead to hairline fractures, ultimately leading to leaks.

Most people also use a nice dollop of the PTFE plumbers tape on the threads. This helps prevent leakage where water can sometimes leak down the threads.

But to be absolutely certain you can tighten the bulkhead with the PTFE tape on and also silicone it in place too. That's what i've done on my 360g bulkhead. But doing it this way is pretty permanent so be sure it's what you want before going ahead.

 

[Bengalcats888]

Awesome.

Thanks.?

 

[jjohnwm]

Silicone is not necessary to get a bulkhead to seal perfectly if it is tightened as esoxlucius explained. You must make sure that the gasket is on the inside of the tank, and that when tightening you are turning the female-threaded locknut on the outside and not turning the male-threaded "throat" piece extending through the hole. If you turn that male piece you are grinding the gasket between it and the tank wall and can possibly damage the gasket and cause a leak. It's also important to not overdo the tightening beyond what was suggested. If you are ham-fisted with a couple of pipe wrenches, you can tighten until the gasket literally flattens and squeezes out from between the bulkhead and the tank wall; again, a leak.

Teflon tape isn't needed and doesn't help when applied to the threads holding the two halves of the bulkhead together; these threads never come into contact with water. Teflon tape should be applied to the male threads of whatever fitting you screw into the interior of the bulkhead, and again, no silicone is needed here. I like to install that exterior fitting tightly and permanently into the throat of the bulkhead first, and then insert the bulkhead/fitting assembly through the hole in the tank, installing the exterior bulkhead locknut last. This allows you to get the threaded fitting nice and tight first, without applying unwanted pressure to the bulkhead gasket.

As stated, silicone isn't needed on any of these joints; having said that, I always use it because it makes me feel more confident.

 

[Bengalcats888]

I'm paranoid from previous set up leaking. I ended sealing all joints with silicon.

 

[phreeflow]

I'm paranoid from previous set up leaking. I ended sealing all joints with silicon.

That’s fine and I’m sure it’ll help a bit and give you extra peace of mind but just note that silicone doesn’t adhere well to plastics.

You mentioned that your filter is being made out of a barrel and are having difficulty due to the curvature of the barrel. If so, you may want to look into Uniseals....they should do a better job on curved surfaces than rigid bulkheads.

Here’s a pic of it in use (not my pic).

 

[duanes]

There are bulkhead fittings made for barrels, they have a curvature built in.
In the states I saw them in rain barrel situations, and here in Panama they are used in above ground gravity feed roof tanks, or cisterns.
Similar for use on my roof top tank below.