Sump plumbing question valves and unions

[linkedsilas]

ive been looking for ideas and I’m confused on pictures that I’m seeing.
I have a durso , so 2 bulkheads in the corner.
Why am I seeing union valves right after the bulkheads pipe and then a valve right after.
Why isn’t it a union valve right past the bulkhead so if you had to make repairs you could stop the water from running out?
Wouldn’t water potentially be able to still slip past the pipes inside the tank if I didn’t silicone it in and be stopped by the valve?

 

[ScottieB]

I think I see what what u mean. I have a center overflow otherwise similar to what you describe. In the event I need to disconnect the tank from the sump I can unscrew the union after the water level drops below the weir, then I don’t have to worry about water in the drain pipe.

In reality, it’s probably a good idea to have a ball valve before every union otherwise the union does nothing more then flood the floor if you attempt to disconnect it.

 

[linkedsilas]

I think I see what what u mean. I have a center overflow otherwise similar to what you describe. In the event I need to disconnect the tank from the sump I can unscrew the union after the water level drops below the weir, then I don’t have to worry about water in the drain pipe.

In reality, it’s probably a good idea to have a ball valve before every union otherwise the union does nothing more then flood the floor if you attempt to disconnect it.

This is what I thought
Thanks
I don’t silicone my pipes inside the tank to my bulkheads and knew it wouldn’t make that great of a seal
Problem solved
I also use union valves so I skip the union for that part

 

[PaulPerger]

You may be seeing valves that ARE unions. Mine are like these...

At Marine Depot.
At BRS.

 

[linkedsilas]

You may be seeing valves that ARE unions. Mine are like these...

At Marine Depot.
At BRS.

No, they are def unions and not union valves which is why I was really confused

 

[Firemanreefkeeper]

Usually it's union, then valve to be able to remove the valve for cleaning. It normally isn't for stopping the water from going down to the sump, the valve is used to control how much water goes down and its used on a herbie overflow or bean overflow.