I have a cast iron toilet flange that no longer holds the flange bolts. The area corroded just enough that the bolts will no longer slip into a secure position. The rest of the flange is too secure to knock loose and replace with a closet flange. I bought a hydroseat to secure onto the existing flange, but the problem I’ve run into now is the concrete slab I am trying to secure it to, the area one of the four screws is being screwed into, the concrete has deteriorated. Does anyone have a solution I can follow to secure something to the Existing flange collar that does not include me trying to remove that?

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    Have you tried slipping stainless steel bolts (round-head machine screws-1/4") with fender washers (small i.d. x large o.d.) under the iron flange, instead of "toilet bolts"? May 1, 2020 at 5:29
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    Hello, and welcome to Home Improvement. Would you add a picture of the problem to your question? May 1, 2020 at 9:07

1 Answer 1


Do you have any friends with a wire welder? These little welders work well for filling the holes and retapping.

I usually grind the heavy rust then mark well beyond the holes so I can re drill in the same place. Heat the area around the hole with a torch then using a wire welder Fill the holes with common wire let cool grind flat. Drill and tap then make sure to use brass screws so they don’t have problems.

I have done this probably 2 dozen times with good success 3 or 4 on my own homes one that I know is still good 20 years ago. Several that we still owned for 10 years after and they were fine.

They make kits that you can cut the flange but if there is good metal and you can drop a weld it works better.

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