Close Loop Bulkheads - Silicone or not?

[ReefPig]

I’m at the later stages of build of my new tank, of which I have three closed loops in the system.

Three outlets placed in the base, three returns in the back panel.

Structurally it’s sound, as I’m using double laminated glass panes on both panels, so don’t let this design decision distract from my main question.

I’m getting cold feet about the bulkheads, right now they each use 50mm bulkheads with the rubber seal and tightened down using a wrench as tight as they will go.

I guess my concern is long term, small amounts of movement/vibration from the pump, servicing etc, will move the plumbing over time.

I was always told not to use silicone sealant for bulkheads, but to tighten them down well.
I guess my question is, would it be any harm if I used reef safe silicone around the outside of the bulkhead onto the glass, to act as an extra barrier before the rubber seal.

I wouldn’t use it between the rubber and the glass, as this could impede it, only externally on the bulkhead.

I’m trying to build a 10+ year tank, and don’t want to be worrying about it all the time.

Thoughts?

 

[ryanjohn1]

I personally wouldn’t. Just make sure gaskets are wetted with water and tighten

 

[FishOkay]

Personal preference I would say to this. I can't see any harm in it on the dry side but also can't necessarily see the point in it lol. They are made to last without the need for sealant but if it helps you not worry then why not is what I say.

 

[DanyL]

I never had a closed loop system, so my opinion is not based on personal experience.

That being said - closed loop bulkheads aren’t meant to be serviceable, unlike those found in the overflow box which you can drain if needed.

Also - from what I’ve seen, closed loos are usually built with the pump mounted rather close to the bulkheads, which would transfer vibration forces regularly.

Given that, in my opinion there’s no harm to seal it with silicone as an extra precaution, and I would also ensure the closed loop pumps mounting method is solid and stiff to prevent and reduce potential vibrations.

 

[MrGisonni]

I wouldn't. Just use thread tape and tighten that sucker down.

 

[mfinn]

When I have installed bulkheads for all applications ( closed loops, drains, returns ) I use the correct bulkhead for the hole drilled, make sure the gasket is new and in perfect shape. But I put a tiny ring of silicone around the base of the bulkhead where it fits through the glass, just to fill the small space around the threads. inside the glass in the hole.
Probably doesn't do a thing, but it makes me feel better.

 

[ReefEco]

Hey there - first i would make sure you are using schedule 80 bulkheads, rather than the black plastic ones (if your hole diameter allows). I would not use the silicon - but I'm not really sure it matters that much. It does worry me that you have tightened the bulkheads "as tight as they will go", which could lead to cracking of the flange down the line. Usually you tighten a bulkhead hand tight, then one half turn with a wrench. This still makes seal, but is not so tight that things may crack down the line. I won't get into the wisdom of putting bulkheads on the bottom of a tank, but what you could also do is slather the external nut and threads with silicon when you tighten it - then immediately slather more on top (silicon won't adhere to dry silicon) so if the bulkhead does leak, it essentially has a backup seal. This will make turning the nut more difficult, but as someone already said, a bulkhead on the bottom of a tank isn't meant to be serviceable. Let the silicon dry for at least a week before adding water to the tank...

 

[ReefPig]

Thanks everyone for your comments.

I spoke to my tank builder, who also provided the bulkheads.

Little bit different in the UK, as we don’t have schedule 80, but these things are heavy duty, link below. Particularly the flange side, it’s heavily reinforced, unlikely to ever split etc.

I have tightened them pretty tight, but not excessively, I wasn’t hanging off the end of the wrench.

Anyway, the tank builder guy said they should be tightened really well with a wrench, but that I shouldn’t use silicone.

VDL 50mm bulkhead