Bathtub overflow - is it a vent?

[darisler]

In my "dewalt" plumbing guide book the drawing for a tub seems to imply the tub overflow is acting as a vent to protect the trap for the tub. (Tub drain connects to san-tee and overflow, and then to p-trap). At least, they are not showing the vent in their book.

Do I then connect to another san-tee and up to roof vent, and down to sewer? or is that not needed?

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So assuming the worst, do I always need to have a vent on the other side of a p-trap?

 

[Standardairconditioner]

The tub overflow is not a "built-in" vent for the tub drain.

A vent protects the water behind it, so the water in the p-trap does not get sucked out.

 

[Sponsor]

 

[Jadnashua]

The vent must be AFTER the p-trap...the overflow and vent are performing different tasks.

 

[darisler]

In my "dewalt" plumbing guide book the drawing for a tub seems to imply the tub overflow is acting as a vent to protect the trap for the tub. (Tub drain connects to san-tee and overflow, and then to p-trap). At least, they are not showing the vent in their book.

Do I then connect to another san-tee and up to roof vent, and down to sewer? or is that not needed?

*************
So assuming the worst, do I always need to have a vent on the other side of a p-trap?

 

[darisler]

Okay thanks makes sense. So I have a bit of a rough-in problem. Tub is on main drain goes to basement slab. Vent line and overflow are too close, only 3" apart. I have 8" ceiling joist to work with. I am next to. 2x6 "water wall" but I have to get the p-trap in and vented.

There is about a 2' offset between the slab drain and the tub drain. So my plan is to jog both the vent line and the tub drain (after p Trap) horizontally for those 2 feet, then into a sanitary tee on down to the basement connection.

I don't see how to connect the vent up any sooner, no room to make the jogs plus limit on 135 degrees of bends...

Does it sound reasonable? I will dry fit and take pics...

 

[Jadnashua]

The vent line must go vertical before the drain turns down, and depending on the diameter of the pipe, within a certain distance.

Second thing, dry fitting pvc pipe is only going to give you a rough idea...the pipe will NOT go to the bottom of the sockets of a fitting until you add the cleaner and cement (which literally melts the plastic). The sockets are tapered, so you will not get the pipe in all the way as when you glue it together, so your positioning will off a bit compounded each fitting.