I own a cabin in the woods, it has a existing septic tank. We just placed a camper trailer up top from it about 300' away. I'm temporarily letting a friend live in it so I wanted to run 3" pipe from the camper waste tank down to the septic tank. My question is: will it flow freely all the way down to the septic tank or will I have to vent it along the way somehow? Thanks for any help - someone told me with back pressure it wouldn't drain completely?

Hmmm... numbers are a little off there, Tom....I know how that goes!!

br3ntl3y (https://www.askmehelpdesk.com/members/br3ntl3y.html) at 1/8" pitch per foot of pipe a 300' run of pipe requires a minimum of 37.5" of pitch... just over a 3 foot fall between the camper and the septic tank. I would strongly suggest running this in 4" PVC over that long a run.

You will also need to install cleanouts at the camper, along the pipe every 50 to 75 feet, and at the septic tank just before the connection is made to the septic tank piping into the tank... just in case a clog should develop!

In terms of venting, you should only need to vent the fixtures of the camper (or have a main vent stack at the camper) and waste will flow just fine. Think of it this way: there are all kinds of homes with driveways that far exceed 300' and none of them have additional vents installed on their drain lines, right (they do have additional cleanouts every 50-75 feet)? Like I said, as long as there is a vent stack and/or the camper plumbing drains are properly vented there should be no issues here!

Mark

Thanks guys I'm an electrian not a plumber! This hill goes down almost @ a 40% grade. I mean we are talking a height difference of probably 50 ft. @ the end. I think it will go down like a rocket lol. I get the clean out thing but this is very temporary! Plus my tank holds 40 gallons. With tank treatment the waste will turn to basically water by the time it needs to be emptied. Idk maybe one @ the end? I think I'll be good then right? If u guys need electrical help ask me thanks!

Also I already got 3" pipe. I paid $120 for 400' so that's definitely what I'm using!

I said 40% grade its more like 30% if that makes any difference but the drop is a good 50 to 60 ft from top to bottom almost the same decline.

Numbers were way off Mark. Thanks for the correction. While a clean out is called for a vent is unnecessary. Blame my error on advanced age and diminished brain power. Tom

I only hope I am half as sharp as you are in my 80s, Tom!

br3ntl3y (https://www.askmehelpdesk.com/members/br3ntl3y.html), I'd like to see if you can reduce the extreme pitch you are talking about... too much and could end up leaving solids (waste and toilet paper) in the pipe over time. Here, if you can offset and lay the pipe so it almost level for a few spots along the run you will end up with a better, more trouble free installation. Otherwise, you should be fine for the short term!

Good luck!

Mark

OK I really can't do that its only until winter I'm not even burying the pipes. It'll be fine. Thanks a lot guys!