I have a timberframe home with a SIP roof with a standing seam metal roof. While the roofer was here I installed two 2 inch plumbing vents which I thought were adequate for my 2 bathroom house. I now know that the cross sectional area required for the vents has to equal the area of the building drain 3 inch diam. It will be very difficult to enlarge the existing holes to accommodate larger vent pipes. My proposed solution is to remove the ABS 2 inch vents( outside diam 2.5 inches) and replace them with copper 2.5 inch outside diam yielding an increase in vent area due to thinner walls. Is this solution acceptable/reasonable? Can I then transition to ABS/PVC for the rest of the DWV? Thanks for any input. I did propose it to the BI but got an indeffinate answer. I’m hoping for more info to convince him.
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Is it your house? Do the drains work without sucking out the traps? If the answers to both are yes, then I'd leave it.
I believe that only the house vent needs to be the size of the house drain. The other bathroom is OK with a 2" vent.
I agree with link. If it's your house leave it. Does the inspector not like it? I do agree that the inside dia of a copper pipe is alot bigger. It's not rocket science. But the copper will be pricey. Could you use a thinner walled PVC?
How about adding a studor vent under a sink somewhere? Are air admittance valves allowed in your jurisdiction?
Or else, how about just adding another vent pipe?
Edited 2/2/2008 10:15 am ET by Matt
I don't think, percentage wise, you're adding enough to make a difference. Are you having problems with the system?
Mike
just dont flush all the toilets at the same time.
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two ways to screw up concrete 1) concrete driver 2) concrete finisher
I'd ask to see that in writing - code passage writing, that is. You're entitled to that info and the BI is required to furnish it without any additional charge. Doesn't matter if (s)he doesn't like the venting, if it's code-approved it must be accepted.
Most plumbing codes, today, accept smaller diameter vents because of the lower-flush water closets.
Increasing the inner diameter at the roof-termination won't help unless you replace the entire length to where it connects with the 3" or 4". At that point, you might as well install the larger diameter ABS vent, which would cost a great deal less than copper.
Many areas of the US permit the use of air-admittance devices to help prevent trap siphonage & (s)he may be inclined to allow that if you're construction is virtually beyond the stage where you have reasobable access to the existing 2" vents.
What did you end up doing to resolve this problem? Yes... some of us are actually interested... :-)
To recap- I undersized the vents when I installed 2-2inch diam abs pipes thru my sip and standing seam metal roof. The required cross sectional area for a 3 inch building drain is slightly over 7 sq in. The abs has an outside diam of 2.5 inches. It was going to be very difficult to try and enlarge the 2 vent holes given the sip panels and metal roof. I did convince the BI that by replacing the abs with 2.5 inch outside diam copper that I gained sufficient cross sectional area due to the thinner wall thickness to greater than the 7 sq in of the building drain. What I will do is have copper only for the short section thru the roof and transition to plastic of the the required diameter inside the house. Copper.org has technical info on all piping including the outside, inside diam, wall thickness for different grades-k.l,m etc. also lists the net cross section of the bore. Thanks for asking.
Was Chris S your inspector?
He just got hired on in Redmond, or maybe Kirkland, not sure but no biggie.
Wa state goes by the UPC.
The UPC states that your vent must be equal in cross sectional area to the waste pipe going out------ you are correct on that.
AAV's cannot be a part of this equation.
2.5" pipe is a listed pipe size with the UPC with a cross sectional area of 4.9" squared.
3" pipe has a cross sectional area of 7.06" squared.
2" pipe has a cross sectional area of 3.14" squared.
The 2.5 + the 2 gives you a cross sectional area of 8.04" squared, which is almost a full square inch bigger than your waste pipe which meets the UPC code.
That 2.5" must run all the way back to where 2 pipes that equal the cross sectional area are joined together. It can be any material that is listed UPC---- pvc abs copper iron etc etc etc.
“The world is a dangerous place, not because of those who do evil, but because of those who look on and do nothing.” —Albert Einstein
In our area (Indiana) the code requirement for the 3" vent exiting the roof must be for weather-related issues (probably a concern with snow or ice/sleet closing off the vent opening). My reasoning is because you are allowed to transition immediately below in the attic to a smaller size vent line.
If it ain't broke, don't fix it, just open it up to see how it works!
In NC we used to have a 3" stack but that changed around 2002 - which I think is when we went to the (NC modified) IPC 2000.