distance from trap to vent

[vdotmatrix]

the existing bathroom sink's trap is 32" from the vent and or drain behind the toilet.

I am remodeling the bathroom and putting in a new vanity on the adjacent wall.

i will have to extend the the water supplys and drain along the wall an aditional 2 feet to the corner and turn 2feet to the middle of the wall which will be the back of the new vanity.

i read something somewhere that the distance from the trap to the vent can't be more than 5 feet? is this true in Northern Virginia?

It's sometimes better to be lucky than smart.

[LazyPup]

The answer to your question will be determined by what spcific code is in effect in your jurisdictiion and that may vary from community to community.

To compute the maximum lenght of a waste are you have to consider the type of fixture it serves and what is the minimum trap size for that fixture. In your case we are examining a bathroom lavatory that reqires an 1 1/4 minimum trap size.

The waste arm pipe must be a minimum of the trap diameter and a maximum of one trade size larger.

All drainage pipes under 3" require 1/4 in per ft pitch.

The bottom of the pipe at the trap weir may not be higher than the top of the pipe at the point where it attaches to the vent.

To compute the maximum length divide the pipe diameter by the required pitch and the answer is total feet of developed lenght of the pipe from the trap weir to the vent opening.

I.E. An 1 1/4 pipe divided by 1/4 inch per foot yeilds a maximum of 5 feet, however, there are a couple options you can consider on a lavatory drain.

If you increase the waste arm pipe one trade size to 1 1/2 inches the maximum lenght is now 1 1/2 divided by 1/4 = 6 feet.

There is another option that can be used on the lavatory. You can get a 1 1/4/ 1 1/2 trap. It is really an 1 1/2 trap with a reducing compression ring to fit the 1 1/4 tailpiece.

You would now have an 1 1/2 waste arm which would yeild 1 1/2 divided by 1/4 = 6 feet, or you could opt to then increase the waste arm pipe the permitted one nominal trade size which would be 2 inch.

2 inch divided by 1/4 inch would yeild a maximum distance of 2 divided 1/4 = 8 feet.


The Uniform Plumbing Code takes into consideration that a portion of the waste arm is filled with water therefore they have derated the maximum lengths.

Uniform Plumbing Code Maximum Trap Arm distance:

1 1/4" pipe 2 ft 6 in.
1 1/2" Pipe 3 ft 6 in.
2" pipe 5 ft

[vdotmatrix]

wow THANK YOU VERY MUCH FOR THIS INFORMATION!!!!!! I have been searching all morning for something anything on this subject....from the vent stack to the corner is just less than 5 feet, then it turns the corner and goes another 2 feet to the trap. So from the lavatory trap add a 2" pipe for 2 feet, a 2" elbow, a section of 2" pipe to meet the drain pipe maintain the proper pitch which will 1.75 feet below the weir and almost to floor or stud level behind the toilet....poof! all of maybe 7 feet.

quote:Originally posted by LazyPup

The answer to your question will be determined by what spcific code is in effect in your jurisdictiion and that may vary from community to community.

To compute the maximum lenght of a waste are you have to consider the type of fixture it serves and what is the minimum trap size for that fixture. In your case we are examining a bathroom lavatory that reqires an 1 1/4 minimum trap size.

The waste arm pipe must be a minimum of the trap diameter and a maximum of one trade size larger.

All drainage pipes under 3" require 1/4 in per ft pitch.

The bottom of the pipe at the trap weir may not be higher than the top of the pipe at the point where it attaches to the vent.

To compute the maximum length divide the pipe diameter by the required pitch and the answer is total feet of developed lenght of the pipe from the trap weir to the vent opening.

I.E. An 1 1/4 pipe divided by 1/4 inch per foot yeilds a maximum of 5 feet, however, there are a couple options you can consider on a lavatory drain.

If you increase the waste arm pipe one trade size to 1 1/2 inches the maximum lenght is now 1 1/2 divided by 1/4 = 6 feet.

There is another option that can be used on the lavatory. You can get a 1 1/4/ 1 1/2 trap. It is really an 1 1/2 trap with a reducing compression ring to fit the 1 1/4 tailpiece.

You would now have an 1 1/2 waste arm which would yeild 1 1/2 divided by 1/4 = 6 feet, or you could opt to then increase the waste arm pipe the permitted one nominal trade size which would be 2 inch.

2 inch divided by 1/4 inch would yeild a maximum distance of 2 divided 1/4 = 8 feet.


The Uniform Plumbing Code takes into consideration that a portion of the waste arm is filled with water therefore they have derated the maximum lengths.

Uniform Plumbing Code Maximum Trap Arm distance:

1 1/4" pipe 2 ft 6 in.
1 1/2" Pipe 3 ft 6 in.
2" pipe 5 ft

It's sometimes better to be lucky than smart.

[LazyPup]

There is one other consideration. You must have a minimum of two pipe diameters from the 90 in the wall to the trap weir.

I would run the two inch in the wall, then turn out with a 1/4 bend and install a 2 x 1 1/2 reducer bushing in the 1/4 bend, then stub out a minimum of 3 inches of the 1 1/2 pipe to the trap adapter.

Also, be careful when selecting PVC fittings..

PVC pressure fittings are rated by degrees and may not be used on the drainage system.

Drain, waste and vent fittings are rated by the fraction of a circle, thus a DWV 90 deg elbow will be properly identified as a 1/4 bend.

[vdotmatrix]

quote:Originally posted by LazyPup

There is one other consideration. You must have a minimum of two pipe diameters from the 90 in the wall to the trap weir.

I would run the two inch in the wall, then turn out with a 1/4 bend and install a 2 x 1 1/2 reducer bushing in the 1/4 bend, then stub out a minimum of 3 inches of the 1 1/2 pipe to the trap adapter.

Also, be careful when selecting PVC fittings..

PVC pressure fittings are rated by degrees and may not be used on the drainage system.

Drain, waste and vent fittings are rated by the fraction of a circle, thus a DWV 90 deg elbow will be properly identified as a 1/4 bend.

So there...i was reading my plumbing book ( B&D) and i think my solution to this thing is to branch the vent stack behind the toilet with an auxillary vent towards the sink a few feet and come down and tie into the existing sink's drain with a waste T and then continue on turning the corner and tying into the new sink...sound like a plan stan?

It's sometimes better to be lucky than smart.

[LazyPup]

You can make your vent that way but you can not use a sanitary tee to connect the vertical drop to the horizontal pipe. A tee can not be placed on its back with the side opening point up.

To connect the vertical drop to the horizontal line you must use a Wye & an 1/8 bend. There is another fitting called a combo, that is a combination of a wye and 1/8 bend all in one fitting.

[vdotmatrix]

quote:Originally posted by LazyPup

You can make your vent that way but you can not use a sanitary tee to connect the vertical drop to the horizontal pipe. A tee can not be placed on its back with the side opening point up.

To connect the vertical drop to the horizontal line you must use a Wye & an 1/8 bend. There is another fitting called a combo, that is a combination of a wye and 1/8 bend all in one fitting.

thank you your feed back is dearly appreciated!. i thought this phase of the project was not going to happen but it went from bleak to do-able! luckily the vent stack and drainage is easily accessible! thanks again. maybe pictures later!

It's sometimes better to be lucky than smart.