Drain Slope

I got this from Google,

Minimum 1/4" of fall per foot on 2" pipe or smaller.
Minimum 1/8" of fall per foot on 3" or larger.

1/2" per foot is Maximum.

The above is just an Info, Thanks.

John

Hi John....

I believe you found the only exception to the rules I posted earlier.

MUST be IPC code...all others that I know of require as I posted...1/4" per foot 3" and smaller, 1/8" pitch per foot 4" and larger.

Always seems to be some exception to every rule! I swear!

I know I wouldn't go with only 1/8" pitch per foot on a 3" toilet line...just seems to be asking for trouble.

Have good day all...

MARK

I agrre with you that's why I said an Info only, Thanks.

John

I too wanted to know the answer to this riddle of the "bubble". I took a 4' level and put it on a level surface, and elevated one end exactly 1 inch (1/4" a foot). It works out to 1/4 bubble, and with a 1/2 inch raise it "just cracked" the bubble (1/8" a foot).

Hi Fenniecp:

If you want a 1/4" per foot of pipe and you are using a 4 foot level I believe it is easiest to tape a 1" piece of anything and read the 4 foot level as LEVEL each time you take a reading....then no guess work about where the bubble is...

Guarantees that 1/4" per foot every time (or 1/8" per foot if using 1/2" block on 4 foot level).


MARK

Oh I absolutely agree, or use a 6' 2x4 with a piece nailed to the end. I was just curious what it worked out to.

[quote] rickj

If you have got a line of sight between your Point A and Point B you can run a string a line between the two using stakes. Run the line 1' above the grade to make sure discrepancies in grade do not interfere with the line. Use a spirit level to make sure the line is level between both points. Measure the starting height at Point A and the distance between the two points. For a 3" pipe multiply the distance between the points by 1/4" and for 4" pipe use 1/8" (check local building codes to see if they deviate from this standard). Use that sum to measure down from Point B, making sure to add the 12" for the line height).

Before backfilling make sure that the slope is uniform and even by using a spirit level. Take note of where the bubble sits and check for any points where the bubble is not sitting in the same position. Raise or lower these areas as needed. Take care that the underside of the pipe is sitting firmly on sand before backfilling.

Too little slope will leave waste sitting and building up in your pipe and too much flow could make the water separate from the waste (especially on 'watersaver' type toilets) and cause the same problem. (On non-city sewer systems: septic beds, etc. Too much pipe slope will increase the pressure on the tanks and force a higher flow rate then desired on your system).

All the best!

Mark nailed it! Pipes 2" and smaller = 1/4" to the foot while pipes 3" and up require only 1/8th per foot fall. I use a level and just crack the bubble on the big stuff and give it a little more for the 2" branches.
If I am held to zero slope I use a transit. Cheers, Tom