Bulkhead disintegrated.

Erasmus Crowley · Sep 13, 2020

I just wanted to share. About a year ago, I had a bulkhead start leaking a bit. One night, I decided to tighten the nut under the bulkhead and it just kept tightening down further and further, and then the whole pipe came downwards about a quarter of an inch. I didn't have the resources to fix the issue, and it was just leaking into the sump, so I let it ride. After that was a lot of procrastinating. Well this weekend I finally got around to replacing the tank and plumbing and I thought I would share what I discovered, and what I think might have caused it.

Some background info. When I was setting up the plumbing, I thought it would be nice to have standpipes coming straight up from the bottom of the tank. I thought it would give the fish things to swim between. I have a deep sand bed. So there was no overflow box, and the bulkheads were buried under the sand, which is why I procrastinated so hard and for so long. There was just no way to maintain the bulkhead without completely replacing the tank.

After the old tank was removed, I was excited to finally figure out what happened. Turns out that the top of the bulkhead that sits on the wet side had become ridiculously fragile. I found it completely severed from the threaded part of the bulkhead and it was in multiple pieces. I could easily break the plastic between my fingers. The rubber gasket seems to have been dissolved entirely. I didn't find any sign of it in the sand. The only thing that had been holding the pipe in place for at least several months was the sand, which had hardened around the pipe.

Also worth noting was that I had used silicone sealant on the rubber gasket before I attached it and then buried it.

So some combination of either the silicone sealant, and/or the anoxic environment under the sand caused the rubber gasket to dissolve to nothing, and the plastic of the bulkhead failed entirely.

I won't be doing either of those things again.

Billdogg · Sep 13, 2020

I've never heard of that happening before! You are VERY lucky - if it had failed completely you would have drained the entire tank.

Failure of a bulkhead (usually just leaking!) is why you should never have a bottom drain without a overflow box of some sort. It is also why many choose to go with a overflow of whatever sort near the top of the tank - it limits the water loss when the worst case happens.

Erasmus Crowley · Sep 13, 2020

Billdogg said:
I've never heard of that happening before! You are VERY lucky - if it had failed completely you would have drained the entire tank.

Failure of a bulkhead (usually just leaking!) is why you should never have a bottom drain without a overflow box of some sort. It is also why many choose to go with a overflow of whatever sort near the top of the tank - it limits the water loss when the worst case happens.

Yep. Lesson learned. I knew all that in theory before this, but i REALLY know it now. My replacement tank does have an overflow box and much simplified plumbing that can all be disassembled and replaced without having to go through this nightmare again. I've never heard of a bulkhead failing this way either, which is why I thought I would post about it. Just to let people know that it can happen.

A small update. As I was cleaning off the old tank to transport it; I did manage to find the rubber gasket. It was still adhered to the glass at the bottom of the tank, and it looks almost like new. So it was just the plastic of the gasket itself that failed.