Drain Slope

RickJ · Sep 21, 2006, 04:49 AM

We've always used 1/4" and I've heard from many that this is the standard. I've never heard of 1/8" per foot.

I'd consider going 1/8" per foot if it were a sink or other liquid only drain, but certainly not for a toilet.

mwarney · Sep 21, 2006, 05:00 AM

Quote:

Originally Posted by RickJ

We've always used 1/4" and I've heard from many that this is the standard. I've never heard of 1/8" per foot.

I'd consider going 1/8" per foot if it were a sink or other liquid only drain, but certainly not for a toilet.

Thanks for clearing that up. I'm not sure where I read it but somewhere I remember instructions to maintain between 1/8" and 1/4" per foot. A plumber once told me to have "Half a bubble" on the level.

RickJ · Sep 21, 2006, 05:04 AM

I'd far more trust a ruler than a level for something as important as slope. You sure don't want to be re-doing it later.

allozier · Sep 21, 2006, 03:43 PM

I usually use 1/4 in per foot which equals about a quarter bubble on a nine inch torpedo level. But with these 1.6 flush toilets they sell these days I have found that 1/4 in tends to let the water go by and hold the waste back and eventually build up and stop up. So I tend to run a little less slope on lines with toilets on them. You might check wih other plumbers to see what they think but it works for me.

speedball1 · Sep 21, 2006, 03:56 PM

When we rough in for drainage we just crack the bubble on a level. In all the hundreds of rough ins we have done in my area we have never had a problem using this method. Only once, when I put in a super market was I held to using a transit on the refrigeration drains. I consider half a bubble to be too much fall. Regards, Tom

mwarney · Sep 22, 2006, 02:58 AM

Quote:

Originally Posted by speedball1

When we rough in for drainage we just crack the bubble on a level. In all the hundreds of rough ins we have done in my area we have never had a problem using this method. Only once, when I put in a super market was I held to using a transit on the refrigeration drains. I consider half a bubble to be too much fall. Regards, Tom

Thanks Tom, Any idea what that interprets to (in terms of slope per foot)?

speedball1 · Sep 22, 2006, 06:53 AM

"Any idea what that interprets to (in terms of slope per foot)?"

I never really figured it out mathematically but my guess would be 1/8th inch to the foot. Cheers, Tom

speedball1 · Oct 8, 2008, 10:52 AM

Quote:

Originally Posted by RickJ
I'd far more trust a ruler than a level for something as important as slope. You sure don't want to be re-doing it later.

Sounds complicated to me Rick,
Would you explain how that goes for the rest of us. The only time I've ever used a ruler is when I was held to zero slope putting in super market reefer lines and had to use a transit to do it. Regards, Tom

massplumber2008 · Oct 8, 2008, 11:03 AM

By the way Mwarney...

Plumbing codes in the USA mandate that pipes 3" and smaller get 1/4" pitch per foot minimum.

Pipes 4" and larger can have a minimum 1/8" pitch per foot.

If not on commercial job using a transit level to keep track of slope I take a 4 foot level and I tape a 1/2" block of wood at the very end of the level which is equal to 1/8" pitch per foot so that when I place the level on the 4" or 6" underground pipe, for example, and get a level reading from the level I know I have a properly pitched pipe for sure!

Good luck!

MARK

Drain Slope

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