How do I replace cast iron pipe from concrete septic tank to holding tank?

November 26, 2010, 10:11 am
Hey, I have a pump up septic system that has worked great for 30 years. main tank holds all sediment and has an overfolw with bafflle and the brown water flows gravity feed to holding tanks with pump out to leach field. Recently I noticed my main tank overflowing and i assume the overflow pipe is corroded and blocked as blocked artery:) How do I replace with PVC and make a tight seal where the pipe enters each concrete tank. The distance is only about 14 inches and i don't believe i can us a hub, this will have to either have a flange or some way to seal coming from main tank. or is their a cement I can use to putty the PVC to concrete opening? Thanks again for your help.
Before starting the work, have both the septic tank and the pumping chamber pumped out. At this point, you may be able to snake out the line between the two, which will be much easier than replacing it. If it does need to be replaced, dig up the area, including about 6 inches below the pipe. The pipe will likely need to be cut to get it out. Make 2 cuts, take out the center piece, then pull out the other two pieces from the tanks. Do not make the hole in the tanks any larger than you need to. Add about 2" of 3/4" gravel to just below the tank openings. Replace the old cast iron pipe with schedule 40 PVC pipe. Be SURE the pipe drains the correct direction! Seal the pipe into the tanks with Quikrete and allow to cure according to the package directions. Fill around the pipe with 3/4" gravel - should have at least 2" below and 2" inches above the pipe. Then cover the pipe back up with soil - you'll want to mound the cover dirt slightly to allow for a bit of settling.

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