I’m remodeling a master bath room and need to extend the 1 1/2 drain line for the whirlpool tub 2′. This will put it at 7’8″ from the vent. 1’8″ over code. This is not going to be inspected. Moving the vent is going to be a major hassle. Will the drain still work if I go over by 20 inches??
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Randy,
First let me make it clear that I am not a plumber; although I did start out working in the trades as an assistant plumber. Hopefully. someone more qualified will step in and provide you with your answer, but I doubt they will tell you what you want to hear. Venting is probably the most misunderstood parts of the plumbing system. It's purpose (venting) is to equalize the air pressure in the system and to allow air to escape which in turn allows the waste to move through the pipes. There is so much more involved, but the bottom line is without proper venting a vacuum could be created and as a result of this vacuum, the water in the trap could be siphoned out. This will allow sewer gases to enter the living space endangering you and your loved ones. Codes are the bare minimum that you want to build to, they are created for a reason. Just because it is not going to be inspected should not be a reason not to comply. Seek the advise of a licensed plumber on this one. Good luck with your project.
Woodrow
Do you have both the physical access (to change the pipe) and the ability via the code (to stay within compliance) to increase the diameter of the pipe?
If you change the drain (p trap) to a 2 inch drain. The vent can be 8 Ft from vent according to IRC. Only other way would to be, install another vent upright in the wall close to p trap and then tie into existing vent above any sink elevation. Or maybe an Air Admittance Valve.
Yes, I can change out the diameter to 2 in. but, not without a lot of demo as its in the footing. I forgot about those air valves. I think that may be the ticket. Do I only need to be above the trap or is there amin. height? Randy
4 inches minimum above trap arm.
Hey Brownbag thanks a lot. R.Stone
I would suggest you consult a plumber re the placement of an air valve. If you just place the valve 4" above the trap arm you are below the flood level of the tub, risking a rather large puddle of water on the floor and in the walls if the waste line is somehow blocked and the vent fails to hold back the water.
Ralph, Good advise. My client allowed me to downsize a window that gave me a stud bay to run a new vent up and out the roof. Problem solved. Thanks.