Waster discharge pipe size ? - Plumbers say tear up my new slab to up size risers

[kenmac]

Nothing else to the story. Builder dropped that news on me Saturday. I plan on talking to the new plumber directly to understand his concern better. So far, I think 3" is fine based on the opinions so far. Builder only said he thought the plumber was concerned with flushing. Thanks for the insight guys.

you might want to check his credentials .. The new guy may not be certified. (provided your state requires plumbers to be certified) If there are no inspections. he could get by without being certified

 

[Cataclysm]

Seems like now that the builder may have actually FIRED THE WRONG PLUMBER?
3" is fine!

I'm thinkin the same thing about the plumbers. Leave that 3" and hit that lever with confidence!

I would be checking the new plumbers work every single day with a level in hand. The builder is in it to make money. They will use the lowest bidder generally. We get called way to often to fix the budget plumbers money saving short cuts.

 

[bigdeano]

I built a house with 3" and never had a clog in the 5 years I lived in it.

 

[turnkey4099]

I have a 4" main line running the entire 60' length of the house with a 3" riser on each end of the run. Worked fine for 35+ years. If you have a 3" riser to each toilet - that's more than adequate.

Have you checked with the building inspector? There should be specifications for the required riser pipe to meet code.

 

[CurlyDave]

I put 3" in my house in CA and lived in it for 20+ years with no problems.

A modern low-flow toilet uses 1.6 liters/flush. That is a slug of water 14" long in a 3" pipe.

Get a different plumber...

 

[cat fever]

As at least two other plumbers have said and I will also say, you are fine. I have plumbed literally thousands of new homes. There is nothing wrong with what you have stated. It also would not matter with high or low flow toilets, you will have no problems. Below was a quick search for fixture units and line size. As you can see 3" is OK by the "Uniform Plumbing Code."


Search Results
DFU are used to determine the drainage from fixtures and required capacity of sewer service systems
Individual Appliance, Appurtenance or Fixture Minimum Size Drainage Fixture Unit Values (DFU)
(inch) Private Installations
Bar sink 1 1/2" 1
Bathroom (water closet, lavatory, bidet and tub or shower) 3" 6
Bathtub 1 1/2" 2

 

[kidr]

Some would argue that you get an even better flush with 3'' pipe.

 

[Larry Caldwell]

One big mistake amateurs make is to oversize drain lines on the theory that they will work better. Just the opposite is true. A drain that is too large will not scour and is prone to clogs. You want to keep the water velocity fast enough to carry the solids out. Stick with 3", and also use the smallest drains allowed for lavs. Inch and a quarter will be much more reliable than two inch for a sink drain.

 

[TCJatko]

New house, 3" riser to 4" mains, no problems.

 

[Egon]

What are your local code requirements? That is the criteria that must be met.