I am working on a 75 gallon paludarium and have decided to drill it and install bulkheads. I have researched bulkheads and drilling glass but I wanted to run a more specific question by more experienced people before placing my order for the bulkheads, fittings, and strainers.
The bulkheads, as well as their fittings and strainers, that I am looking at come in slip/slip, threaded inside/slip outside, and threaded inside/threaded outside. First I was just going to go with slip/slip but I do not want to have to destroy the bulkheads if I glue the plumbing together and decide to change the plumbing later. So I looked into the threaded options, thinking that I can just use plumbers tape for the threaded fittings outside of the tank going to and from the sump. Would that be the smartest option? I originally don't expect there to be enough water pressure to require gluing the outside fittings but the possibility of a minor leak eventually starting there scares me.
The bottom glass is tempered so the holes would have to be drilled low on the back glass of the aquarium. The plan is to use three of the same sized bulkheads, one connected to the pump to return water and two for draining water to the sump. The outside of all three bulkheads will be connected to 90 degree barbed fittings for attaching vinyl tubing that runs down to the sump. The return fitting will be angled straight down as it is receiving water from the pump, so it would be best to have a straight tube with no extra turns. While the two 90 degree drain fittings would be able to be angled slightly up if need be so that the highest point of the vinyl drain tubing will dictate the water level, allowing me to tinker with the level of the water inside the paludarium. I keep going back and forth on where I would like to have the water level so I would like to have the freedom to control the height using the drain tubing rather than the bulkhead holes. If angling the 90 degree fittings up is not advisable, I could loop the drain tubing up the back of the outside of the aquarium to the final height of the water level which would accomplish the same thing. The reason that I am using two drains that are the same size as the return, rather than one drain that is larger than the return is so that the substrate isn't flooded if one drain gets partially or completely clogged. Obviously I will keep an eye on them but you never know when a piece of a leaf or other debris will end up in the water or when a plant decides to go crazy with its roots.
So in summary, the question would be which would you use and why, threaded or slip?
Any other advice, experience or ideas would be welcome as well. I only get one shot at this and would rather have it be a success than a costly learning experience