Proper Bulkhead Installation

[Egon]

Came across this today.
This is really quite easy to do, and can be done with PVC or CPVC fittings. Careful sizing of the penetration hole is the key to success. Measure the diameter of the male thread and select a drill bit that is just slightly larger, but not larger in diameter than the outside of the receiving female fitting. Drill the hole and test fit the fittings by screwing them together. If it is difficult to thread the fittings together, take them apart and clean the threads. Try again. The fittings should thread together until the shoulders of the fittings are tight on the pane of glass or acrylic. Sometimes a dab of silicone will lubricate the threads and allow easy assembly. It is a good idea to have proper size wrenches or two set of pliers to aid in assembly if the fittings are difficult to join. Aquarium-safe silicone applied to the mating faces of the fittings will ensure a water-tight seal.

Don't use silicone

 

[kendragon]

I agree with Egon. Don't use silicone. I did in the past and what happened was the silicone acted as a lubricate causing the gasket to squeezing out from under the bulkhead. The gasket dry will compress in place resulting in more seal area.

 

[dawnmarie]

OK, I'm almost afraid to put this out there.

Sealants , RTV silicone included are usually applied too heavily and not allowed to set up long enough. This applies equally to building an engine, installing a window in your house or installing a bulkhead fitting either in the hull of a boat or in the bottom of an aquarium.
My personal preference is to use a sealant "sparingly"on both sides of the gasket when installing a bulkhead fitting. Tighten the nut finger tight (or barely snug for the neanderthals with a massive grip ). Let it set overnight. This will result in a perfect seal every time.
The hardest lesson to learn is patience.
There is an old saying " There is never time enough to do it right ,but, there is always time to do it over".

If you must install a bulkhead fitting and fill the tank with water immediately, then absolutely install it dry, and don't over tighten. There is far less chance of failure. Otherwise , slow down and get it right the first time.

Sorry if that sounds overly heavy, it's just this old mechanic's opinion.

 

[brianhellno]

I thought applying an aquarium safe lubricant to the gasket and then installing the bulkhead just a bit over hand tight was the way to go. The lubricant is so the gasket doesn't stick to the bulkhead or glass during installation at an angle so it gets an even flush seal.

 

[dawnmarie]

I thought applying an aquarium safe lubricant to the gasket and then installing the bulkhead just a bit over hand tight was the way to go. The lubricant is so the gasket doesn't stick to the bulkhead or glass during installation at an angle so it gets an even flush seal.

Brianhellno, what you describe is essentially the same method I use although lubricant and sealant are not interchangeable terms. Unvulcanized silicone sealant is quite slippery and when used in excess and or overtightened can cause the gasket to distort or squeeze out causing a leak. Egon and others are right that used incorrectly silicone is a bad idea. The other variable is defining "Finger Tight " or "Hand Tight".
My definition is run the nut on by hand until it squarely contacts the bottom of the tank and stop. After 24 hours tighten an additional 1/4 to 1/2 turn depending on the coarseness of the threads.