Installing new sewer/septic line....question

jel7October 5, 2008

I am installing a new four inch pvc line to my septic system.

The line will be three feet in the ground, initially.

What is the best way to establish the new line with correct fall or 1/4 inch per foot and keep it from

settling off correct fall as dirt is returned, over the

new line?

I am thinking of putting a few four inch blocks under the new line.

Please suggest ways to prevent this new line from settling.


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Unless your house is extremely large and has more than 3.5 bathrooms it is highly unlikely that you should have a sewer line greater than 3" however. to answer your question, you may not put stones, bricks, wooden blocks or any other hard object under the pipe. Properly you should backfill slightly and pack dirt under the pipe to bed & support it in place but be careful here. The pipe MUST BE laid in such a manner that the writing on the pipe wall is clearly visible at all times. If your inspector cannot read the writing on the pipe he/she has the right to condemn that section of pipe and require it be re-positoined or replaced before approving the job.

    Bookmark   October 5, 2008 at 6:08PM
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lazypup, Thanks for your response and advice.

You are correct. The sewer line leaving my house is three
inch but the sewer line entering the septic tank is four
inch (the way tanks are installed in this area).

I go from three inch to four inch and make the line four inch.

Am I correct that 45 degree elbows can be used anywhere as long as the fall is constant?

Does it matter how close 45 degree elbows are to one another?

I plan to go from three inch to 4 inch and drop two feet with a 45 degree enbow then start a run of about 10 feet before another 45 degree elbow for a right turn lining up with an existing 45 degree down 4 inch pipe.


    Bookmark   October 6, 2008 at 7:28AM
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Obviously you have firmly made up your mind to run the line in that manner, and there is nothing in the codes that would prevent you from doing so, on the other hand, unless you enjoy frequently snaking clogged sewer lines I would never do it that way.

    Bookmark   October 7, 2008 at 9:02AM
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The inspector I dealt with didn't mind large drops, but insisted that the last 10' entering the tank be pitched no more than 1/4" per foot. He claimed that too much pitch at the tank allows water to enter at too fast and stirs up the tank contents. Who knows;-)
As Lazy-pup says, if you can avoid using the 45's it would be smart to do so. 3" pipe should be flexible enough that you can make gradual bends. Of course if your tank is close to the house this might not be possible.

    Bookmark   October 7, 2008 at 6:25PM
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