What's the thread size on a 1" bulhead?

[NickRummy]

I have a 1" bulkhead on my tank and seems like a rather odd setup. The standpipe is a slip fit but on the bottom it's threaded internally and externally. I had a 1.5" ID hose clamped to the outside thread but it wasn't a good fit and I want to convert it to a rigid setup. I can't figure out what thread size this is though? It's about 1.5" if you measure it but a 1.5" fitting was too large?

The inside threads worked for a threaded fitting for a 1" pipe. I used that for now but it REALLY cut back on my drains capacity.

Any idea what fitting I can get for the outside threads? Is there a common size I'm not aware of?

[RokleM]

1" bulkhead is built for 1" PVC, whether it's slip or thread. The "external" thread is for the nut, not plumbing.

[NickRummy]

Could it still be used for the plumbing though? Makes sense that it's not for it and for the nut that attaches it. With the 1.5" hose attached it flowed a lot more water and more quietly. With the 1" rigid pipe attached it has been reduced quite a bit.

[RokleM]

Technically there's nothing stopping you, but that's not the purpose. It outside/nut has a completely different thread than standard PVC. If it's a quality bulkhead, it should have the same rough internal diameter of the PVC, so it shouldn't be restricting any more than the rest of the drain itself.

What size tank and how much return (GPH) are you using? Typically this is only an issue if 1) the tank was designed wrong and really needs multiple drains and/or a larger single drain or 2) if the person is trying to push WAY too much water through the sump (3-5x is sufficient for most, or whatever your skimmer can adequately process).

[NickRummy]

It's a 65g with a 20L sump. I'm running a Mag 9.5 but have it restricted A LOT with a ball valve. Probably close to %75 closed? when I was running the 1.5" ID flexible hose it was maybe %25 closed?

[RokleM]

That's doable, but much more pump that is needed for that tank as you're aware. Open you're probably at about 600-700 GPH. Personally I'd keep an eye out on a much smaller and more efficient pump in the meantime. If you wanted to stick with a MAG, a 3 or 5 would be a better option, or an Eheim would be a good replacement brand.

[chimmike]

I think the problem is you're trying to use a durso drain. That's restricting the flow you can utilize from the pump you have. Unfortunately you probably can't enlarge the hole in the tank to use a larger bulkhead.

I'd suggest not using the external threads on the bulkhead. Not that it'll matter if you use larger piping after the bulkhead, the 1" bulkhead restricts the flow anyways.

[NickRummy]

Then how can you explain me being able to run the return less restricted when the 1.5" flex hose was attached to the outside of the bulk? It definitely made a difference. Maybe the threaded male adapter that goes into the threaded bulk is the major restrictor?

It probably was overkill how i had it before. I estimated probably 500gph being moved through the drain. I think the mag 9.5 was 720gph with 5' head height. Now I might be 200-300?

I just got rid of a mag 7 too.