Steeply sloped waste pipe

**Bruce Ramsey** · 01-28-2010, 07:23 PM

I seem to remember that waste pipe is allowed to be installed vertically or near horizontal (1/4" per ft slope) only. I read something years ago that said steeply angled pipes cause water to flow too quickly and can leave solids behind forming clogs.

The past two days the main waste line was angled 45-60 degrees.

Can you have a sharply angled waste line?

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**Michael Thomas** · 01-28-2010, 07:44 PM

As I remember it, any slope between 45 degrees and vertical is acceptable.

But I don't have a cite for that.

Mark T. Denton · 01-29-2010, 08:00 PM

On this short of a run the slope should not be a problem. Anything more than 45 degrees is considered verical. What might be a problem is the lack of support. Both the PVC & ABS need supports 4' o/c. I don't see any in the photo's, but they might just be out of view. I would also check the glue on the ABS joints. I seem to remember there have been issues with it. Good luck.

**Ken Rowe** · 01-29-2010, 10:35 PM

Originally Posted by Bruce Ramsey

I seem to remember that waste pipe is allowed to be installed vertically or near horizontal (1/4" per ft slope) only. I read something years ago that said steeply angled pipes cause water to flow too quickly and can leave solids behind forming clogs.

The past two days the main waste line was angled 45-60 degrees.

Can you have a sharply angled waste line?

It depends if it's black water or gray water. If it's only for gray water it shouldn't be a problem.

**Mike Schulz** · 01-31-2010, 02:41 PM

steeply angled pipes cause water to flow too quickly and can leave solids behind forming clogs.

I remember that also. but if it's to steep the **** would just fall through the pipe not needing water. Maybe the rush of water could suck traps dry. Would like to here more on this though.

**Markus Keller** · 01-31-2010, 05:32 PM

I wouldn't be concerned about those short runs and see them as essentially vertical drops. 1/4" per foot on horizontal runs as others have mentioned. There should be a hanger on either side of those 45's though for support.

Ted Menelly · 01-31-2010, 07:40 PM

Originally Posted by Bruce Ramsey

I seem to remember that waste pipe is allowed to be installed vertically or near horizontal (1/4" per ft slope) only. I read something years ago that said steeply angled pipes cause water to flow too quickly and can leave solids behind forming clogs.

The past two days the main waste line was angled 45-60 degrees.

Can you have a sharply angled waste line?

Yes you can

**Jerry Peck** · 01-31-2010, 08:20 PM

Originally Posted by Markus Keller

There should be a hanger on either side of those 45's though for support.

Actually, plastic pipe should be supported at spacings of no greater than 4 feet, except for CPVC in sizes 1" and smaller which need to be supported at spacings of no greater than 3 feet.

Plastic piping does not, however, need to be supported at each fitting, although it basically works out that way because if there is no greater than 4 feet between supports there will be two supports near each fitting, or one right at a fitting and the next support within 4 feet of the first support (which would be less than 4 feet from the fitting).

**John Kogel** · 01-31-2010, 10:46 PM

Originally Posted by Jerry Peck

Actually, plastic pipe should be supported at spacings of no greater than 4 feet, except for CPVC in sizes 1" and smaller which need to be supported at spacings of no greater than 3 feet.

I gues string's no good, huh?

A few pics of typical plumber's art for you'all. How many gallons of crud have travelled through that angled copper pipe? None, if it's a vent.

The last one, the drain for the PRVs is propped up with a piece of ABS resting on the flooring at the left elbow. Very creative new construction.

**H.G. Watson, Sr.** · 02-01-2010, 01:12 PM

Minimum slope for trade size is just that, minimum. Ideal provides proper scour (friction), displacement of air, with a minimum of pipe errosion. The norm is to maintain a certain slope for the majority of the run of the drain, fixture branch, etc. and offset adjust at the downstream, as gravity does a good a job of moving solids too (as well as water velocity & friction). IIRC trade size =/< 3 @ 1/4"/ft is a velocity of about 3 ft/second for water.

As long as the necessary and required cleanouts are provided, venting, and support it should not be a problem for drainage, errosion & useful life may be reduced.

A back to basics primer on the subject, this link is to a similarly titled article in PMEngineer (clickable link below). Hope you find it helpful:

Back to Basics: Sanitary Drainage Systems - Feature Articles - PM Engineer____

**Dana Bostick** · 02-01-2010, 01:51 PM

Originally Posted by John Kogel

I gues string's no good, huh?

A few pics of typical plumber's art for you'all. How many gallons of crud have travelled through that angled copper pipe? None, if it's a vent.

The last one, the drain for the PRVs is propped up with a piece of ABS resting on the flooring at the left elbow. Very creative new construction.

There is such a thing as copper DWV piping. Marked in yellow I think. If it is a vent, its wrong. It cannot be below the waste inlet from another fixture.
Dana

**H.G. Watson, Sr.** · 02-01-2010, 02:00 PM

Originally Posted by Dana Bostick

There is such a thing as copper DWV piping. Marked in yellow I think. If it is a vent, its wrong. It cannot be below the waste inlet from another fixture.
Dana

DB,

When I see yellow marked copper I think GAS (or other hazard possibly petroleum, oil, steam, etc.) not sanitary, gray, or storm water; that's what green markings are for (liquids, inherently low hazard).