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Question DetailsAsked on 1/28/2018

how much would it cost to replace 20 feet of cast iron drain line under concrete basement floor in Liberty mo?

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Here are a few previous similar questions with answers which might help you, FYI:

I would be expecting $500-800 in very cheap labor area, probably more toward the $1000 range plus or minus a few hundred in most areas, and possibly into the $1500-2000 range in very high cost areas or if this also involves going through the basement wall and tying into the cleanout outside.

You did not say WHY it needs replacing - if you have had it cleaned and sewer camera run and see it is all corroded out or cracked up, or it was routed out and the router was getting caught up on broken pipe or such at multiple spots, then you know. But if just clogging a lot, might be worth the typically $250-400 to get the entire line routed (my preference with metal pipe) or jetted (which tends to have skipped area issues with many types of jetters) and then a sewer camera run - all the way to the septic tank or street sewer as applicable.

This will remove the buildup of soap scum, grease, and fibers which reduce the pipe inside diameter over time. This is something that should normally be done every 10-20 or so years, depending on how much prolonged hot water discharge (long showers or a lot of clothes washing) there is (a good thing), and how much garbage disposal plant fibers and food grease goes down the lines (a bad thing).

You might find, as a result of the camera run, that it does not need replacement - or perhaps there is just one damaged spot (so maybe $500 range for that repair commonly) - commonly cracking or joint offset where it passes through the foundation because the outside backfill was not compacted right, so that part settles more than the relatively "fixed" part in the foundation, causing an offset joint or cracking.

Also, if your sewer has not been cleaned recently, getting the rest cleaned to the street can commonly alleviate underslab blockage tendencies. This is common where line inside diameter reduction due to grease buildup and such, or root blockage, restricts the flow downstream so the solids tend to drop out as soon as they hit the backed-up liquid in the pipe. This commonly occurs right downstream of the point where the in-house vertical stack turns near-horizontal for the under-slab run. It can also cause blockages at seldom-used wyes like to unplumbed/seldom used downstairs/basement bathrooms or floor drains - with solids backing up into those wyes and partly blocking the wye. This makes that the actual "clog point" but it may actually be caused by the solids hitting and dropping out due to water backup from further down the line, because the flow velocity drops off, keeping the solids from being flushed allt he way to the septic tank or sewer.

Checking for free flow during multiple consecutive flushes or full laundry load discharge at the outdoor cleanout (commonly a place you can see down into the pipe with a flashlight) can usually clarify if the issue is upstream or downstream (or rarely right at) the cleanout. If toilet flush or washer discharge flows freely and in high volume flow through the cleanout Tee or Wye but water then starts backing up in the cleanout from downstream after a significant amount of water goes through (may take several flushes to fill the line and cause backup), then the blockage is downstream of that point. However, if the discharge flow through the cleanout is low and prolonged, more trickling than rushing through the cleanout, then the partial blockage is upstream. If both happen, then you probably have a serious root problem or the line just needs routing / jetting out for its entire length.

As for cast iron or plastic pipe - unless in a highly corrosive environment (like your cast iron corroded out in less than say 40-50 years), I always recommend cast iron under slabs - with flexible connectiopn just outside the foundation wall, and GOOD compaction of the soil under and around the pipe at that point to prevent settlement cracking. Generally, I try for two joints right outside the wall - one say 6-10 inches outside the foundation to provide a good stickout for connection to with a flexible (not rigid or leaded) joint, then another joint with a couple of feet at the cleanout. This makes the piece of pipe just outside the foundation short and flexible (with a joint at each end) so it can move quite a bit before it breaks. For the joint just outside the foundation I prefer a flexible no-hub coupling with corrugated stainless outer protection, like this type -

There are long-reach ones longer than that - more like 8 inches long for 4" pipe with 4 clamps - which provide better flexibility too. Look like this but longer - from Fernco and American Valve and other manufacturers.

Answered 2 years ago by LCD

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