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New plumbing

1K views 6 replies 3 participants last post by  sharp 
#1 ·
New plumbing to be done in a remodel.
I have had different opionions on whether to use 3" or 4" PVC drain pipes. is the 4 really less likely to clog considering the toilet trap is 3" inch? There will be one vent pipe going to the roof for master bath, 1/2 bath and kitchen.
Cost of material is not the issue, but using the smaller 3" would be easier to bury in the walls. Just hate not to use the best long term materials.
Thanks
 
#2 ·
Sometimes, bigger is not better. If there is not enough water drainage, the solids could stop in the pipe. Most houses I have plumbed have 3" until it goes through the foundation wall, and then goes to 4". This depends on local codes though.
 
#3 ·
The toilet TRAP should not be 3" Most are 2" 2-1/8 or 2-1/2.

The drain line is a 3" minimum, however, by water conservation standards today, you will have a lot more issues if you install a 4" drain, due to the fact that a 4" drain needs more water per flush to 'float the solids down the line'

With todays toilets, you are getting less and less water per flush.
 
#4 · (Edited)
Alan. Toilet traps are a part of the toilet bowl, not a separate part. The minimum size of piping under the toilet is 3'. There should be no trap in the piping under the toilet. Not sure why you brought up the word trap since it was not in the original post. Maybe I am just a bit confused about your answer.
 
#5 ·
It was in the original post. Please Re-read.

"is the 4 really less likely to clog considering the toilet trap is 3" inch?"

What I meant to say was that the toilet trap shouldn't be 3" since there isn't a trap in the drainage piping. I guess I probably would have been better off actually just saying that there shouldn't be a trap on the toilet line. I've been plumbing for 3 years now, I definitely know better. :thumbup::thumbup:
 
#6 ·
Alan, my apologies after re-reading the post. I actually missed it twice. Sometimes I forget that the people asking advice, use wording that is actually inaccurate, at least I hope he doesn't have a trap in the toilet drainline. 35 years in the trade, over 10,000 posts in DIY sites and retired and still miss some things.
 
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