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Old 12-28-2012, 07:50 PM   #1
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Drainage Slope - Ontario Building Code

Here is the section in the Ontario building code I'm looking at:

7.4.8. Minimum Slope and Length of Drainage Pipes Minimum Slope

(1) Except as provided in Sentences (2) and (3), every drainage pipe that has a size of 3 in. or less, and every fixture drain shall have a downward slope in the direction of flow of at least 1 in 50.

(2) Sentence (1) does not apply to a force main.

(3) Where it is not possible to comply with Sentence (1), a lesser slope may be used if it will produce a gravity flow of not less than 0.6 m per second

I haven't done SOLID measurements yet but most likely I will be running into this problem. My situation is that I'm running a 1 1/2" drainage pipe under a door that will be covered by a landing. I only have so far I can slope the pipe up in this 8-10 foot run from the slab floor to the opposite edge of the future landing (toward the fixture) before the landing will have to rise above the door sill. But, if I'm interpreting this properly, it will be okay for this to be installed in this way as long as I have a >0.6m/s flow (can test using a glass of water and a stopwatch since I know the length).

Am I on the money here or not? After the landing, the 1/4" per foot is no problem. The water will be carrying mainly dirt and dog hair, I don't want to to slow down too much and create sediment. I would be installing a cleanout in this location if this setup is allowed just in case. See crude drawing below to illustrate. Thanks for any direction...


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Old 12-28-2012, 11:16 PM   #2
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1) Is this installation being inspected by the AHJ?
2) Will this drainage pipe be "easily" accessible via a nearby clean out?
3) Can the slope of the initial line in the "Room with new fixture" be increased to provide extra velocity through the pipe beneath the door?

If (1) is yes, and (3) is yes, then you should be okay by code .
If (1) is no, then you "should" still be okay in practice, whether or not you can get the velocity up, but I'd make sure (2) is YES, just in case.


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Old 12-29-2012, 01:48 AM   #3
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pete 0403 drain slope

The drain slope for 1 1/2 pipe should be 1/4 per foot so the pipe in 8 ft needs to slope 1 inch in four feet 2 inches in 8 ft and 2 1/2 inches in 10 ft. Measure the slope by simply placing a tape measure on the top or bottom of the pipe and calculate the drop. Doesn't matter if it is USA/Ontario the drain physics remain the same and do not believe any code would contradict this fact Hope this helps Mr Leak
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Old 12-30-2012, 01:31 PM   #4
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Thanks for the reply Joe. I will be able to generate enough velocity and there will be clean outs. The drain will usually be handling only the amount of water coming out of a hand sprayer. And there will be lots of dog hair so clean outs will be essential.
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