I'm running 3 inch pvc pipe 20 foot horizontally from my toilet to my septic drain. From the beginning to end of my first 10 foot length I should have a 2 1/2 inch drop from my floor which will give me a 1/4" pitch, I add a coupling and another 10 foot length and I should have a 5 inch drop at the end of my 20 foot right? I have a 4' digital carpenters level which has a angle mode I can set for 1/8, 1/4, 3/8, 1/2, etc, right now my pipe is temporally hanging with a drop of 5 inches from beginning to end at 20 feet which should be correct for a 1/4 inch pitch. I put my carpenter level on and it's only showing an 1/8 inch pitch, I'm not sure if I should go with my 5 inch drop at the end of 20 feet or go by the level, is a carpenters level different from a plumbers level for showing pitch?

 

You could set a stake at the outlet end of the pipe and mark it level then lower the pipe a measured 5".

 

I highly doubt that your level is dependably accurate. 5" drop in 20ft is 1/4" per ft.

 

I don’t have or have ever used one of those levels, but it looks like most of those levels advertise error in measurement less than 0.1 or 0.2 degrees. But it sounds like yours is off by a half of degree if your drop is truly 0.250 in/ft.

But as was already stated in XSleeper post it’s an accuracy problem. Your level (and I guess all of them) can’t measure the angle close enough to hit a true 0.250 in/ft drop right on the head.

Last time I did something like that I think I did like cwbuff says in post #2. I think I just ran a string from end to end and hung one of those little line levels on the string to make sure it was level from end to end. Then measured down at one end of the string and marked the point for the proper drop. I think that’s what I did – but looks like you already got it right, but just are questioning the digital level reading.

 

I shim my level when doing drain piping. If I want 1/4" per foot drop I will tape a 1" thick spacer to the end of my 4 foot long level, or a 1/2" high spacer to the end of a 24" level. Then place the level on top of the pipe and center the bubble. The shim on the end will provide the slope/pitch.

 

The added benefit is since you're supporting the PVC pipe every 4', that 4' level works out perfectly!

 

I re-adjusted my pipe hangers again and put it at a 5 inch drop for 20 foot. Purchased a 10 inch plumbing level that has the pitch marks on the bubble site and with my 5 inch drop it shows me at a 1/4 inch per foot. I guess that digital carpenters level may be good to show angles but not accurate enough for pitch. Learned something new today, use the right tool for the right job, thanks for all help and all the great tips....