Upstairs tub drain in old house

[William Curtis]

I'm pretty new to plumbing, certainly in a house built in 1910. A previous owner had redone the drain system using a mix of the galvanized pipe and PVC, with no real venting unless you count the overflow on the tub. Two upstairs sinks share the same 1 1/2" drain line .Recently the upstairs tub stopped draining almost completely. The clog was at a union of where two types o f pipe joined. (see pic.) I replaced it all with PVC. It flows much better but maybe a little slow still. The picture shows the length of drain pipe as it emerges from the wall in the basement after it has made the trip downstairs two stories. My questions are : 1. Is the P-trap neccesary and productive this far down the line ? 2 . Theres no room to add venting to the tub upstairs. Will it help any to add a mechanical vent either inline along this length of pipe in the basement or off one of the sinks upstairs. Any help is appreciated.

 

[Jeff H Young]

Why oh Why is it plumbed like that? looks like 3 drain pipes. a running trap ? what's going on no room for a vent . at least put an AAV up stairs and a p-trap, how about getting rid of all that gal the horizontal all the way to where it 90s toward the brick. perhaps tie it to the 3 or 4 inch with a combi above the window

 

[Sponsor]

 

[Reach4]

My questions are : 1. Is the P-trap neccesary and productive this far down the line ? 2 . Theres no room to add venting to the tub upstairs. Will it help any to add a mechanical vent either inline along this length of pipe in the basement or off one of the sinks upstairs.

The purpose of the trap is to keep sewer gases from reaching the tub.

The purpose of a vent is to keep the trap from getting siphoned out, preventing the trap from doing its job. An AAV at least 2 inches before the U bend of your new trap could potentially help prevent that siphoning. That will not make your installation meet current requirements, it would be closer if you are not thinking absolutes.

The elbow on the right should have been a medium bend, and the transition from vertical to horizontal, from the tub, should have been done with a long sweep or 45s or 22.5s. The vertical fall, or the distance, to the trap is probably longer than it should be.

 

[William Curtis]

Why oh Why is it plumbed like that? looks like 3 drain pipes. a running trap ? whats going on no room for a vent . at least put an aav up stairs and a ptrap, how about getting rid of all that gal the horizontal all the way to where it 90s toward the brick. perhaps tie it to the 3 or 4 inch with a combi above the window

I replaced all the galvanized with PVC and that hodgepodge of fittings is now a straight shot. Just below the edge of the photo the 1 1/2 " vertical pipe goes to 2" then joins the 3'' pipe next to it which then joins with the other 3"pipe. I plan to put a clean out in the 2" section.

 

[William Curtis]

The purpose of the trap is to keep sewer gases from reaching the tub.

The purpose of a vent is to keep the trap from getting siphoned out, preventing the trap from doing its job. An AAV at least 2 inches before the U bend of your new trap could potentially help prevent that siphoning. That will not make your installation meet current requirements, it would be closer if you are not thinking absolutes.

The elbow on the right should have been a medium bend, and the transition from vertical to horizontal, from the tub, should have been done with a long sweep or 45s or 22.5s. The vertical fall, or the distance, to the trap is probably longer than it should be.

Upstairs the tub drain has about 1 1/2 inches of pipe then it tees to the incoming tub overflow pipe then it goes under floor so I have no room for an AAV vent there. The two bathroom sink drains tie into the drain shortly after it goes under the floor. If I added an AAV under one of the sinks would that help ? I did replace that 90 in the photo with a longer bend .

 

[Reach4]

The two bathroom sink drains tie into the drain shortly after it goes under the floor. If I added an AAV under one of the sinks would that help ?

I don't understand what you are saying there.

I was picturing this, but did not take into account any non-bathtub connections before the U-bend:

 

[Jeff H Young]

send the after pictures rather than the befor or in addition to the befor pics.
why not one pipe going up?