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Question DetailsAsked on 12/16/2014

Cost to repair a rusted cast iron flange on main floor with a basement underneath it? Replace w/a cast iron flange?

A plumber removed my toilet to see if the leak was a faulty wax ring. It wasn't . The flange around it is rusty and a piece broken. With each flush it leaks a little into the bathroom below. Can you replace the old flange with a new cast iron flange? Or is it necessary to cut the cast iron pipe about a foot down in the basement and repair that pipe. Any estimate on a cost?

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1 Answer


Here are a number of links to similar prior questions with a number of answers.

Cost is tougher to estimate - with plastic sewer pipe, working from below, probably about $200-250 to replace the flange and a couple foot section of pipe, assuming there is no significant wood rot preventing placing new 2x blocking to support the flange (which should be supported to keep the pipe from riding up and down with floor flexing, to keep the wax seal tight). If the plumber has an inside pipe cutter, might get it a bit cheaper as can be replaced from above in that case, without opening up drywall ceiling below it. Cast iron is tougher - probably $200-350 range, few plumbers have an inside cutter that can cut cast iron fromthe inside, and plumber most likely does not know how to do a leaded joint so will use a rubber coupler instead. They are not terrible, but last maybe 20-30 years before leaking as opposed to hundreds of years with leaded joint. Make sure if using a rubber coupler that he used a metal-sleeved type - more permanent and more resistant to movement. Look like the first couple shown in link below, rather than the cheaper and less permanent ones further down on page with just bare metal clamps on the rubber. And should be with adjustable screw bands not crimp bands, so can be tightened in future if it starts leaking. For this to be effective, there should be a threaded piece of pipe coming down from the flange, so the no-hub coupling is in the open underfloor area, and make sure he orients it so the screws on the clamps can actually be accessed in the future for tightening if needed.

As far as the flange fix - sounds like the plumber was inexperienced, because there are several ways to fix a broken flange - replacement flange rings which overlay the old broken one (if most holes are intact) and is sealed to it with gasket sealer, bolt-on replacement hub flanges that bolt to top and bottom of old hub flange to provide new bolting places all around, and insert type replacement flange that is slipped down inside the old flange and silicone sealed to it (reduces the inside diameter a bit) - plus of course the above replacement of the flange in its entirety. The latter methods are more commonly used for in-slab failures to avoid digging out a lot of concrete, and are a bit more prone to leak and corrode than a replacement flange so not as long-lived, but can cut your repair cost by 25-50% or so. Alternatives look like this - sleeves and flange replacement pieces, then insert sleeves at second link (with some rings too) -

Google this search phrase - toilet mounting flange repair rings - for how-to's on flange repair/replacement - not that I am suggesting you do it yourself, but the more you know the better you are placed to discuss repair with the plumber - do NOT allow him to just goop it up wioth silicone and callthat a fix, as you commonly see when you are called out a few days or weeks later to fix the scab job.

Note the answers do NOT include drywall repair and painting in the ceiling below, if needed to repair access hole - one or two of the responses address that cost too.

Answered 5 years ago by LCD

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