A Deep Dive Into Toilet Flange Repairs

For an industry newbie the seemingly simple repair of a toilet flange may not be so straightforward. Here’s a look at what you’ll want to keep in mind.

A Deep Dive Into Toilet Flange Repairs

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Editor’s Note: Master plumber Anthony Pacilla occasionally writes “Now What?” features, where he sets up a scenario and uses his real-life experiences to provide problem-solving advice about it.


You sell Mrs. Jones a new toilet since her current one is old. You pull the toilet and find a corroded and broken toilet flange.

Now what?

What seems so simple and straightforward can be frustrating at times for the new plumber, especially when there are tons of variations, ages, conditions, and repair options. Which one should you use in what situations? You look at the broken flange. You go over your options.

Get Clean

You are an artist and you need to work with a clean slate. Get the wax mess off the flange. Shop-vac the crust and use cleaner and a rag to clean the area. Once you have cleaned the immediate work area, get a bucket to set your scrap in to keep your work site clean.

Take An Assessment

There are a few things you need to look over before you get to the actual repair step.

First, look to see why the flange broke in the first place. Is it simply old age or did something cause it to fail prematurely? Many times an uneven floor and uneven setting of the toilet leads to rocking which then leads to a broken flange.

The other thing to look for is the depth of the existing flange. Is the flange too high? Is the flange too low? Most times the flooring guys have put in a new tile floor without having a plumber re-rough the flange to proper height. The tendency is to either double up on the new wax ring or use flange spacers to beef up to proper height. Both of these are wrong and should not be used as a permanent solution. Doubled-up wax rings will leak and spacers will definitely leak. And don’t even think about caulking between spacers. Fight the urge to pull the trigger on these handyman-type repairs.

Cast Iron Flanges

A broken cast iron flange can be a pain to fix properly. Most times the cast iron flange is so thick that the split-type repair flanges are too thin to make an impact, and the full-sized spanner flanges are near impossible to install because cast iron is not easy to drill into. You need to remove the flange and start from scratch.

There is no perfect way to remove a flange but there are a few good ways to try. First, try and drill a series of holes in the lead that is in between the flange and the cast iron pipe. Once you have drilled the lead enough, cold chisel, fight, pick, and pry the lead and oakum out and pull the flange.

Another way — and probably less time-consuming — is to break the flange itself into pieces using a cold chisel and small sledge. Try not to use a flat bar to pry the flange up (especially if you are working with a tiled floor) as it will crack the surrounding tile work. The correct way is to drill the holes as previously mentioned and use an old-school “pitching” tool to pull the lead and oakum out.

Once you remove the cast iron flange you have a few options. There is a nice repair flange that has internal Allen screws where you push the flange down into the cast iron pipe and tighten the Allen screws, making a tight seal. Screw the flange down and you are good to go.

By far the best way to make this repair is to pour a new lead joint with a new cast iron flange. Find a master plumber or journeyman at your company and ask them to do one with you. A poured cast iron flange is not going to rock or move anywhere at all if done properly and is by far the best repair option to replace an existing cast iron flange.

Concrete Flanges

If you run into a flange that is going into a concrete floor, make sure you screw the new flange in with Tapcons, not drywall-type blanks and screws. The blank anchors will slowly pry up with everyday use of the toilet. If the toilet is set in the basement on a raw concrete floor, and the concrete is so uneven that shims won’t do it justice, pour a bed of thinset down where the toilet will sit and set the toilet into the bed and let it set.

Types of Repair Flanges

There are three main types with the new repair flanges. The blue/red pot metal flange, the PVC flange, and the stainless steel flange. The stainless steel flange is king in my opinion. I have seen too many of the blue/red pot metal flanges less than a few years old rotted away and falling apart. The PVC flanges will usually snap and break since plumbers typically use 5/16-inch bolts and make them good and tight. Either that or a customer who moves around a lot could snap the flange. Either way, take a look at how weak that thin part of the flange is.

Miscellaneous Repair Tips

If the hole is too big to screw the new flange down, pull up the wooden subfloor and put a new section in place that is the correct size. If the hole is too big in a concrete floor, dig it up and rough it in properly by stubbing up your pipe, wrapping it in some 3-inch pipe insulation or a corrugated spacer, pouring concrete into the spacer, and then using an internal pipe cutter and gluing your flange down to the new concrete.

If you can’t get screws to bite into the subfloor, consider drilling and using toggle bolts. If you have a thick enough wooden subfloor, consider using a router set at half the depth and make a square impression piece in the existing plywood. Then make that same depth piece out of new wood with a new flange hole and glue and screw it down into the impression you made (the old carpenter’s trick). Every once in a while you will be able to cut out the existing flange flush with the floor and use a socket saver to drill out the old hub. At this point you can glue a new fitting in.

And if all else fails, pour a lead joint. Even on PVC piping. Learn how to do it and use it where you can. No matter what you do, take the time to do it the right way. Don’t take a short cut and bash a PVC flange into a piece of cast iron and caulk it.

About the Author

Anthony Pacilla is a registered master plumber for McVehil Plumbing in Washington, Pennsylvania. He has 22 years of experience in the plumbing and HVAC trades, and has a bachelor’s in business and economics from Thiel College. 



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