Frozen main clean out plugs

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    • #279310

      70 year old house. Plugs not removed at least in the 30 years I’ve been in. Is there any risk in putting a lot of torque to get them unscrewed? I’ve wd-40d them for week or so. There are 3….one at an angle and 2 which are horizontal which I think are a U trap just inside the house. I don’t want to risk breaking the 4″ main which is in concrete up to the work area.

      Note that nothing is wrong. I just like to have things work and be able to inspect and see what’s in there. Should the U trap be cleaned periodically?

      One alternative would be to slice down the middle with a 4″ grinder, with careful hacksaw up to the threads and squeeze the two sections together to free up.

      Or should I just leave the whole thing alone?

      Regards, Ron

    • #300506
      Retired plbg1

      If it is iron pipe you can take a torch and get it good and hot and put a wrench on it and unscrew it.

      Art retired plbg

    • #300507

      I’m sure RP has had more experience (and better results) than I’ve had trying to unscrew CO plugs from old bell & spigot CI pipe. I’ve tried everything, including the torch and torque approach (with a BIG pipe wrench and yard long cheater pipe). It will either work or crack your drain (especially if the pipe is old and corked). When such pipe cracks, it’s usually in the most inconvenient place to repair, like in a wall or in the foundation…

      The safest way that I’ve found is to try heating the pipe on the outside where the plug goes in. You need a good source, such as acetylene with a broad flame tip, and apply gentle even heat all the way around, and try to avoid heating to the point of melting the lead caulking in nearby joints. Then use a 24″ or 36″ pipe wrench (without a cheater) and pull fairly hard but not too hard. If that doesn’t loosen the plug I use a 2 1/2″ diamond hole saw attached to a Hole Hawg drill to cut out the center of the plug. Then I make four equally spaced cuts radially from the hole in the plug to within 1/8 inch of the threads in the fitting, using a reciprocating saw with carborundum blades). Light taps with a 1/2″ cold chisel easily free the pieces of the plug (don’t let them fall into the drain). Then get a plastic plug and install it with Teflon tape and pipe dope. This approach always works, but the equipment costs a lot (the diamond hole saw alone is about $100). If you really want to do it yourself and can justify about $600 in tools that you may or may not use again, go for it.


    • #300508

      My call to a plumber indicated that it was only necessary to remove the plug on the U trap on the side most inside the house. The cleanout plug can wait until it’s necessary to roto-root the line to the street, and only the one U plug removal is needed for access to the trap.

      The recommendation is to knock the plug out with a cold chisel being careful not to let pieces fall into the trap.

      I still think a 10,000 rpm grinder with a 4″ metal cutoff wheel to slice down the middle up to the threads would also work.

      As far as replacement plugs, the city plumbing inspector wasn’t too keen on the plugs with the lead threads, feeling they didn’t give as good a seal. I forget if he recommended another type of plug, but I’ve also heard about a plastic plug.

      Regards, Ron

    • #300509

      I finished the job of removing one of the frozen plugs on the U trap next to the clean out plug on the 4″ sewer pipe going out to the street. (only 1 plug needs to be removed which is the one furthest into the house)

      Although I was told by a plumber that I could just knock it out with a cold chisel which is the way apparently it’s generally done, I opted for an approach with less pounding & risk.

      With a 4″ 10,000rpm rotary grinder with a metal cutoff wheel, I sliced through on each side of the nut almost up to the edge. It was pretty thin at the center. I used a vacumn cleaner to catch any filings.

      I clamped a vice grip to the nut & sliced the other two sides and the nut unit came nicely out. With a hacksaw, I carefully cut the 4 slits almost to the edge and the two center pieces easily came out.

      With the support gone, the two remaining sides pulled away easily. It looks like a thread was leaded into the pipe opening and a cap screwed into that, but it was all frozen together and never would have unscrewed with a wrench, no matter how much wd40 one used.

      After cleaning out the sludge in the U trap, I installed a 3 1/2″ rubber expansion plug with a wing nut for easy access in the future.

      I probably didn’t have to do this job, as it wasn’t plugged up nor was there a lot of sludge in the U trap, but I feel better keeping an eye on it and having easy access for the 1st time in 30 years.

      Thanks for all the prior advice

      Regards, Ron

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