External Overflow Box: Why All the Unions?

[TangerineSpeedo]

I will give you a few reasons why you should also that were not covered here so far.
1. As you assemble your plumbing your angles are not going to be perfect. Unions allow for a few degree tweeks so your plumbing/tank/overflow is not stress with undue pressures.
2. Maintenance and access. As your tank matures, you can have biological build up in your pipes which will affect flow. This can be sludge or mussels, tubeworms etc.
3. You may have to move your tank. Whether it is an emergency or to another room/home, you do not want to spend a lot of down time.
4. If your tank is running and you install and glue in a union, you must wait 24 hrs. for the glue to off-gas... so not ideal for a running tank.
Another pro tip, is on unions coming out of your overflow, make sure they are high enough that if you have to take your tank off of your stand, you can set it flat on its base.
With the cost of unions at less than $5 each, should be a no brainer if you are thinking of the future.

 

[twentyleagues]

Yeah, you could take the entire box off to get room to work. I'm just curious if that permanent union end can fit through the overflow box when replacing a bulkhead/ gasket.

If not I'm guessing you would need buy an entire new union just to get the end piece?

This is one of my main concerns/hold ups with putting a union in during initial build. I'm worried the bulkhead is one of the most likely spots to fail/leak and I don't want to have to throw away an otherwise perfectly good union.

You have a valid point there. If you develop a leak on one of the bulkheads going to the drain pipes that union will need to be cut off if its glued to the bulkhead. I use unions but I typically leave room to cut the pipe should I need to.

 

[ReefingwithO]

I don’t know about anyone else but pvc that’s been in use for years has a high probably to shatter or crack for me when taking pvc cutters

 

[twentyleagues]

I don’t know about anyone else but pvc that’s been in use for years has a high probably to shatter or crack for me when taking pvc cutters

Valid been there done that.

 

[Razorbacks]

Follow Up: Ok you guys convinced me. I put a union on each drain pipe fairly close to the external overflow but left room for cutting in case I ever need to change bulkhead on the overflow. The comments about cleaning the lines and also about how they shatter with PVC cutters after a few years caught my attention.

However, another major factor became apparent the minute I started doing the plumbing. Even to dry fit without glue you need to be able to turn pipes a bit this way or that. I realized I was putting a lot of pressure on the main tank bulkhead when I did that and it was just a scary risk to be taking. I loved being able to disconnect the union 10 or 15 times during the pluming process while I dry fit and glued one piece a time and got my angles right.
Additionally, I always planned to have at least one union on the lines and I was able to plumb a short enough run that there was no practical reason to add a second beyond this spot.

I also found a solution for my concern about the overflow bulkheads leaking. Prior to starting any cementing, I filled the external overflow with water and plugged the drains with PVC pipes taller than the box. This let me check for leaks and both leaked heavily. I put the the gaskets on the wrong side! Even after I put them on the correct side they had leaks. I got out my pipe wrench and gave each about a quarter turn and that did the trick. Then I cemented my first pieces which included the unions.