Bulkhead/Fuge issue

What kind of glue should I use? It's an acrylic tank, trying to seal the the bulkhead's material.

Oh, and I do have an overflow from the DT, but this bulkhead is on the back of my sump. I was considering how to seal up the hole where the bulkhead is, and just run the return out of the top.

 

I use this stuff from Home Depot that is marked aquarium safe... I've used it on glass, plexi, etc. and it works fine.

M

 

Alright, so I dried out the bulkhead, cleaned it, put a whole bunch of the silicone onto the threads and into the gap between the threads and hole in the tank, and tightened to the same tightness. It oozed out on the nut side, so I smoothed it out. The outer side never ended up oozing, so I just put another layer out there and smoothed it too.

So, what am I looking at for the cure time? The full 24hrs?

 

I do 48hrs just in case when I use silicone. Maybe the threads are stripped and not creating a good tight seal. The silicone should work.

 

Here is a sticky I did for a couple other reef forums.
The important things to remember are the gasket always goes on the flange side regardless if that is inside or outside the tank, if its next to the nut water will migrate through the threads. Always install the gasket clean and dry, never use and lubricants or sealants.

Bulkhead tips:

1. Always install bulkheads clean and dry, no silicone's, teflons or thread lubricants. Silicone's and lubricants cause the gasket to scoot out or not seal properly. Have you ever removed an old automobile windshield or other gasketed glass? The rubber vulcanizes to the glass with time and creates a perfect seal without any help.

2. Before installing the bulkhead take a few minutes using a jewelers file, nail file or pocket knife and clean any excess flashing off both the male and female threads and from the flat gasket mating surfaces. This is a common source of leaks.

3. Always install the gasket on the flange side of the bulkhead, never on the nut side, regardless if its inside or outside the tank. Installing the gasket next to the nut will lead to leaks. Hand tighten only with maybe 1/4 to 1/2 turn additional, no more.

4. When using threaded bulkheads, again clean the excess flashing from the threads and valleys and use a small amount of teflon tape or better yet the stick or crayon type of thread lubricant designed specifically for PVC treads. These can be found at Lowes, HD, Ace and all hardware stores under names like Laco, Permatex and others.

I use this one and have since the 1980's with great success.
LA-CO: Product Detail - PLASTO-JOINT STIK® - Plastic Thread Sealant
It stays pliable forever and does not tear or roll out of the threads like teflon tape. My swimming pool plumbing up to 2" was all installed with this in 1983, outside in Phoenix AZ and its still pliable to this day!

5. Never support any pumps or piping from a bulkhead, always use supports so weight is not on a bulkhead and gasket causing differential stresses on the mating surfaces.

6. Never screw anything to the external threads of a bulkhead, these are not standard tapered pipe threads and will leak. They are there to screw the nut on is all and are not normally even a standard diameter like 1" etc.

Hope you get some use out of this.

 

Ah dang, I already have the thing sealed up with silicone. Lots of it.

Would this be a long term problem, that it would cause the gasket to slip?

 

Usually if the gasket is going to scoot out or slip it does it right away. It may cause long term issues with sealing though if you ever have to tighten it up later as the silicone may break loose and shift then.

Dry gaskets vulcanize or bond to the glass over time. My motto is, "If its worth doing, it worth doing right the first time".

 

Yeah, I don't think I have the time to wait for vulcanization though. The thing wasn't dry (kept leaking), so it wouldn't have happened on its own under these circumstances. The gasket really didn't have any silicone under it, just what I put around the outer edge as a second seal. The oozing really happened in towards the tank, not on the outer side.

Do bulkheads ever have to be retightened if they're tight enough to begin with? I could see that being a headache if tightening is part of long term maintenance.

 

The nut will loosen up sometimes, especially if you used any lubricants or teflon and the sump gets shifted or you remove a pump often for maintenance. I always try to have plenty of room around bulkheads to tighten or even remove/replace them in the future. When I built my current stand I used hole saws and cut the holes in the plywood top for the internal overflow box bulkheads. I am glad I wet tested everything in my garage before disassembling everything and moving it into the house. I discovered there wasn't sufficient room to get to the bulkheads so I used a jigsaw and cut out a much larger area so I can get my hands or a basin wrench in to tighten them now. A sink basin wrench is a lifesaver for bulkheads, it has a swivel head and can be used at all angles.

Check the face of the flange and the threads for excess flashing or plastic molding scrap, I'll bet that is what is causing your leak. File it smooth and the leak goes away without overtightening the bulkhead which is the other major cause of leaks.

 

So, the bulkhead already doesn't smell like vinegar anymore. Isn't that supposed to be a decent indicator of silicone being dry? I'll leave it until at least 10 tonight anyway, but if it's dry or nearly dry now, I'll do the testing tonight for sure, instead of waiting until tomorrow.

I would check it again, but I have it already siliconed in its place. I didn't see anything on the face that wasn't smooth when I looked at it when I first got it, and before I installed it, though.