Edge case about slope

[rollingcodeset]

Hello, first time poster here.

I've done a fair bit of research and found that generally a fitting is only rolled for venting.

If the Y of a combo were rolled to say 15 or even 30 degrees, at this exact point it would be greater than 1/4" slope.

If this were not allowed then I would also think using 22.5 degree fittings for vertical to vertical transitions would also not be allowed as this too would be greater than 1/4" slope but less than 45 degrees.

Taken the code to its literally meaning it would seem rolling wyes for drainage lines would only be allowed to within 1/4" slope and anything greater would be prohibited.

The code only seems to imply this when it comes to preventing siphonage in trap arms,

I have seen many answers on this that rolling a wye for a drainage line greater than 1/4" slope but less than 45 degrees is not "necessary" for a drainage line as opposed to a wet vent. But it does not seem to be talked about in terms of exceeding the slope requirement for drainage lines.

Any elucidation on this would be greatly appreciated, thank you.

 

[GReynolds929]

1/4" per foot is minimum slope, more is not prohibited except for trap arms as that would cause venting issues. Generally rolling a wye or combo is done for venting purposes as it puts the takeoff for the vent above centerline of the pipe. 45° and greater is considered vertical for DWV purposes. Your generally not going to be rolling a pipe or fitting at 15°-30° cause fittings don't come at those angles. A drain can be vertical and make offsets with no problems.

 

[Sponsor]

 

[Sylvan]

1/4" per foot is minimum slope, more is not prohibited except for trap arms as that would cause venting issues. Generally rolling a wye or combo is done for venting purposes as it puts the takeoff for the vent above centerline of the pipe. 45° and greater is considered vertical for DWV purposes. Your generally not going to be rolling a pipe or fitting at 15°-30° cause fittings don't come at those angles. A drain can be vertical and make offsets with no problems.

11.25 , 22.50 45.00 deg 60 deg fittings available for rolling offsets "drainage fittings" Not very common any more as too much math is involved.

we also use crooked threads for various amounts of pitch for drainage of steam condensate lines.

In cast iron 1/32 bend (11.25) 1/16 bend = 22.5 1/8 bend 45 deg etc

I used 1/16 pitch more then 100 times

TABLE 704.1

SLOPE OF HORIZONTAL DRAINAGE PIPE

SIZE (inches)​	MINIMUM SLOPE (inch per foot)​
21/2 or less​	1/4a​
3 to 6​	1/8a​
8 or larger​	1/16a​

 

[rollingcodeset]

1/4" per foot is minimum slope, more is not prohibited except for trap arms as that would cause venting issues. Generally rolling a wye or combo is done for venting purposes as it puts the takeoff for the vent above centerline of the pipe. 45° and greater is considered vertical for DWV purposes. Your generally not going to be rolling a pipe or fitting at 15°-30° cause fittings don't come at those angles. A drain can be vertical and make offsets with no problems.

Right so let's say that rolling greater than 0 and less than 45 is done for a drainage line, is this something that an inspector (UPC) would flag? I have seen a lot of people make the argument that slope greater than 1/4" results in solids separating from the liquids because it's too fast for the water but it's not enough to overcome the friction of waste.

 

[Sylvan]

Right so let's say that rolling greater than 0 and less than 45 is done for a drainage line, is this something that an inspector (UPC) would flag? I have seen a lot of people make the argument that slope greater than 1/4" results in solids separating from the liquids because it's too fast for the water but it's not enough to overcome the friction of waste.

The "inspector" needs to go back to class if they think will leave solids behind.

NYC had the "greater NYC toilet change out" to conserve water

All toilets were 3.5 GPF or more and the soil lines were sized by a much more gallons .

The majority of plumbers thought this would be a money maker with stoppages due to less volume and scouring action with the new code requirements of 1.6 GPF .

If the sewer system had no bellies or other obstructions to impede the flow then stoppages never occurred

 

[John Gayewski]

Right so let's say that rolling greater than 0 and less than 45 is done for a drainage line, is this something that an inspector (UPC) would flag? I have seen a lot of people make the argument that slope greater than 1/4" results in solids separating from the liquids because it's too fast for the water but it's not enough to overcome the friction of waste.

There's nothing in the code for an inspector to flag. It's not a thing.

The only maximum slope is for combination waste and vent systems. I think that max is 1/2 per ft. It has nothing to do with solids, it's for air flow reasons as the vent is also the drain.

 

[Jeff H Young]

Rollingcodeset, I think you might be grouping things together we have no maximum fall in most drainage situations however trap arms have boundrys I cant tell you in inches per foot or degrees but we know 1 pipe diametor of fall is the max fall on that trap arm. Rescently I saw that one code requires combination waste and vent systems to join a conventionaly drainage by between 22.5 and 45 degrees.
But generaly out side of horrizontal wet venting, or combination waste and vent systems, and trap arms . MOST cases dry venting only needs not have reverse fall , and drainage no maximum fall .
By the way when Im hand digging a trench to cut a wye in and the connection is 3 ft deep or even18 inches deep Ill roll a wye up to avoid digging with no shame of it not being proper nothing wrong with that .