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Drain Cleaner Debate

DEAR TIM: You're completely wrong in your past column about using Drano for clogs. If it doesn't unclog immediately, it stands in your drain and the acid erodes your pipes. At least, this is the case with older homes with galvanized iron and copper parts. I've got the bills to prove it. Dave Werner, New York, New York

DEAR DAVE: It might not be obvious at my website unless you go digging, but among other things I am a licensed master plumber. Over the years, I have developed a pretty good understanding of drain cleaners of all types. You are correct that some drain cleaners are acidic. Some are very dangerous acids that should only be used by professionals and even then with very great care.

Drano's active ingredient is sodium hypochlorite - chorline bleach.


Author's Note: At the time this original column was written, the previous statement was true. The latest information available from the manufacturer now states the formulation has been changed and the active ingredient is lye - sodium hydroxide.


It is not acidic by any means. It is actually a base and has a pH of 10 or greater. Yes, chlorine ions can be corrosive to certain metals if they are in *constant* contact with the metal over a *long* period of time.

If your theory is right, then I need you to prove it. I will assemble a metal drain p-trap of your choice made with any traditional plumbing metal you pick: galvanized iron, copper, cast iron or lead. Then, I will ship it to you and you prop it up and fill it to the brim with pure Drano. I guarantee you a dinner for four at the restaurant of your choice in NYC that the Drano will not eat a hole in the metal.

Your bills are from years of wear and tear on the drainage piping in your home. Drainage pipes actually do corrode and wear out over time. When a clog finally happens in an old pipe, the combination of drain cleaners and aggressive mechanical drain cleaning activities can easily poke a hole in a pipe. I have seen brass p-traps where the metal has become paper thin over time from normal wear and tear. Push a wooden toothpick into the bottom of the p-trap and presto you get a leak.

There is a natural way to keep your drains clean. It just takes a few minutes once a month as well as a couple of friends. Read my past column on this ingenious method that has worked for me for years.

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3 Responses to Drain Cleaner Debate

    • You can use it if you want because most older homes have metal drain lines. But Draino is a lightweight and no substitute for taking the trap off under a sink and inspecting the branch drain line to remove sludge and rust buildup. If the branch arm is galvanized pipe, you'll likely never open up the drain line.

  1. Hey Tim, glad I found this, thanks. Just replaced both 1.25" p traps connected to 1.25" galvanized pipes from two sinks to a t shaped pipe. That t drops 2 feet, turns 90 degrees then runs horizontal for about 12 feet to a 90 degree taking it 8.x feet below the slab. I know the clog is from the t to the horizontal because the washing machine isn't flooding lower on the same pipe.

    So far its been about an hour with Drano on both drains. Any predictions if the clog will clear before something bad happens? I will rinse all I can if it moves but I think I might have made a mistake doing this. I'm assuming the pipes are original 1957, new to me for 6 months.

    I'll let you know with pics if needed. I have before shots with timestamps.

    If it helps, when I filled one sink then let it drain, all kinds of rust and mineral looking stuff came up the other sink. I would guess that had something to do with ptraps, but plumbing is still magic to me. Couldmt day.

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