Union thread to bulk head thread??

Mele__Reef · Jun 8, 2017

In the process of designing a blueprint for my hard pvc plumbing on a SCA 50 gal. My question is, is it safe to connect a threaded union to my threaded bulkhead? Or should I cut a piece of pvc pipe and slip it in the bulkhead then connect the union to the pvc that sticks out from the bulkhead? What's the best way for this? Any advice is greatly appreciated thanks.

Ocelaris · Jun 8, 2017

You can connect anything you have room for, but typically bulk head outside threads aren't standard, so a threaded nipple would be required inbetween the bulkhead inside threads and threaded union. Just use Teflon tape between threaded connections and you'll be fine.

Personally I would connect a elbow to the bulkhead and then use the union going down so it doesn't stick out so much.

ReeferBob · Jun 8, 2017

Do NOT connect ANYTHING to the bulkhead outside threads! These are intended ONLY for the large plastic nut that secures the bulkhead to the tank. Use the slip fittings.

Any other threaded fittings tend to leak btw they are very hard to get not to leak. I suggest all slip fittings. I also suggest a short stub PVC slip piece coming out of your bulkhead and then into a PVC compression fitting on that. You'll love the convenience of a compression fitting. You can rotate the plumbing at will within that fitting and it doubles and a union.

Mele__Reef · Jun 8, 2017

Thanks @ReeferBob. So, is it safe to use pvc cement/glue for the slip piece coming out of the bulkhead? Or will dry fitting be enough? Thanks.

ReeferBob · Jun 8, 2017

Amele8 said:
Thanks @ReeferBob. So, is it safe to use pvc cement/glue for the slip piece coming out of the bulkhead? Or will dry fitting be enough? Thanks.

On the outside of the tank (bulkhead down) you must use the PVC cement. But you should not use any PVC on the inside (overflow compartment), just set your drains into the bulkhead. It doesn't matter if they leak a little.

Ocelaris · Jun 8, 2017

Before we write off threaded completely, let's put a little nuances to the argument for or against.

I've replumbed my entire house in pvc, pex, copper, brass. Hundreds of feet, and probably a thousand fittings. Threaded fittings done right (with liberal Teflon tape) and the right level of force for the respective fitting is completely leak proof.

With that said my bulkhead fittings are glued because they're under the tank. If I had an overflow above or near water level I would have considered threaded.

Threaded leaks are dependent on the installation, and shouldn't be shied away from when there is an appropriate need. Glue/sweat joints are often foolproof, but you shouldn't treat them as infallible as I've had those fittings fail, but more often with unions you forget to put the nut on the bulkhead BEFORE you glue them to union and then have to buy all new fittings and start over.

Mele__Reef · Jun 8, 2017

Got it! Also my setup came with a 1" drain and a 1/2" for my return. Is it possible to upgrade the the return side to 3/4" do you recommend that? Or would the 1/2" maintain more pressure. I will be running a 2 valve manifold for a media reactor and algae scrubber. Thanks for helping me out here. I really appreciate it ! @ReeferBob

Mele__Reef · Jun 8, 2017

Thanks @Ocelaris

ReeferBob · Jun 8, 2017

Amele8 said:
Got it! Also my setup came with a 1" drain and a 1/2" for my return. Is it possible to upgrade the the return side to 3/4" do you recommend that? Or would the 1/2" maintain more pressure. I will be running a 2 valve manifold for a media reactor and algae scrubber. Thanks for helping me out here. I really appreciate it ! @ReeferBob

It isn't possible. The bottom of the tank is tempered after they drill the hole so you cannot re-drill it. If you have a standard 2 tube corner/back overflow compartment I suggest doing a Herbie style drain using both holes as drains and then going over the back for the return. You will get much higher flow than a Durso style with no noise. But, 1/2" will flow plenty of return water to feed your drain.

Ocelaris · Jun 8, 2017

I used both of these for my drain like reeferbob suggested, works great and is nearly silent. The only downside is Then you have a pipe and over the top which makes having a screen top difficult. But I felt that it was worth it.

Mele__Reef · Jun 8, 2017

That's a great idea! @ReeferBob. What size pipe should I use for my return? Also, since my drain is 1" and my stock return is 1/2". Which one should I use for the emergency overflow? Thanks

Mele__Reef · Jun 8, 2017

@Ocelaris can I see what yours looks like so I can have an idea?

Ocelaris · Jun 8, 2017

Sure

Mele__Reef · Jun 8, 2017

Nice! What size pipe did you use for your return? @Ocelaris

Ocelaris · Jun 8, 2017

It's 3/4" pipe for the return, It fit most of the hose fittings fine. Technically the bigger the better, but at a certain point the flex tube is very stiff. You can see I also have a separate 3/4" tube for the uv sterilizer that I added later, and for my water changing station. Some is threaded, but the permanent stuff is glued.

It's not the cleanest, but it gets the job done.

Mele__Reef · Jun 8, 2017

Great I'm definitely doin the herbie conversion. Going to draw up a diagram of what my plumbing is going to look like. I'm also going to run a 2 valve manifold for a media reactor and a algae scrubber. I'll post the diagram to show you what I came up with when I finish it. @Ocelaris.

Ocelaris · Jun 8, 2017

I would strongly suggest a few things: gate valve on the main drain (ball valve is too coarse), a check valve on the manifold so that you don't siphon too much water back when you turn off the pump. My returns are below the water level so when I turn off the pump, if I didn't have a check valve it would raise the water level in the sump to almost over flowing, and definitely overflow the skimmer. Most of the cepex ball valves have unions on them already, so that saves you a part.

If you think you'll tinker with the manifold a lot, the cepex ball valves that brs sells are really awesome. Though they are really pricey. My home depot ones are about 1.5 years old and getting pretty hard to turn. But the ball valves take a lot of space. In the case of a manifold the threaded fittings can save you space somewhat if you use bushings and street fittings.