Garage Floor Drain Slope

[redeyedfly]

Are there any requirements for slope of garage floor drain piping?

The floor drains typically are piped to a sand/oil separator which is an indirect drain, i.e. it provides an air gap. The drains are never trapped or vented. So if you don't quite make 1/8" per ft in fall is that a code violation? (>4" pipe)

 

[Beniah Naylor]

Commercial or residential?

 

[redeyedfly]

Commercial

 

[ICE]

The slope on waste pipe is supposed to facilitate scouring which keeps the pipe clean. A floor drain in a garage might seldom see enough flow to encounter scouring. However, less than 1/8" is just too flat.

 

[redeyedfly]

Agreed on all points ICE. However, I'm looking at a deficiency of ~3" in 60"+ of fall; I'm not worried about it from a practical sense.

I can't find any code requirements for the slope of an indirect drain and wanted to see if anyone here knows of a section I missed.

 

[ICE]

I am not familiar with the IPC. Looking at the indirect wate section 803 in the CPC I find no information related to slope of the pipe and a lot more is not there. The rest of the code still applies to the indirect drain pipe….not just the slope.

 

[Beniah Naylor]

I got nothing in the IPC either.

Section 713 Computerized Drainage Design indicates to me that there could be a little flexibility for an engineered design - if you are confident it will work, maybe you can get it approved by negotiating that angle. The fact that PVC pipe has far less friction on its interior than cast iron, and way more corrosion resistance, I would think that you could get away with a little under the 1/8" slope for what you are doing, as long as you don't take it too far.

Also, check out the user note at the beginning of Chapter 7.

There is nothing relating to slope in Chapter 8 Indirect Wastes.