Calcium and Lime Clog In Cast Iron Pipe

I have a shower on the lower level of the house that is installed directly on the slab. The plumbing is cast iron and is buried under the slab.

The drain, specifically the trap, is clogged up with calcium and/or lime scale and deposits. I was able to manually scrape this crud off of the side of the pipe between the drain pan and the trap. I was also able to punch through the clog at the trap with a metal rod. The deposit breaks up relatively easily and I have the drain flowing again.

What can I use to completely remove the calcium and/or lime deposits from inside the trap? I thought of CLR, but the specs on the company website say it shouldn't be used on cast iron. I'm concerned that anything I pour in the trap will also corrode and possibly damage the cast iron pipe as well. I just want to clear the drain, not jackhammer the floor.

I've also thought about using vinegar to soften the deposits and running a pipe snake through the trap.

I appreciate any help.

Vinegar is acetic acid. It will promote rust if it is left there for very long. It can be neutralized somewhat with baking soda. I think your best bet is as you mentioned, vinegar and a snake.

Hard water scale is rock hard; you'd be using a hammer and chisel. Dried out soap scum, shampoo, hair and lint acumulation is much more likely.

Hardness scale wouldn't form in a drain pipe, the velocity is too slow plus, most of the water in a shower is hot water and for all practical purposes the hardness scale is in the water heater tank.

Get a small piece of it and place it in some vinegar and see what happens. If it disolves then you can use it on the problem areas but remember if you pour it in the drain other than what sits in the trap, will only flow along the very bottom of the pipe and will do little for any other part of it.

Gary Slusser said:

Hard water scale is rock hard; you'd be using a hammer and chisel. Dried out soap scum, shampoo, hair and lint acumulation is much more likely.

Hardness scale wouldn't form in a drain pipe, the velocity is too slow plus, most of the water in a shower is hot water and for all practical purposes the hardness scale is in the water heater tank.

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Did you have some advice as well? Otherwise I don't see the point of your reply.

PS - It is not "Dried out soap scum, shampoo, hair and lint acumulation". I had to use a long screwdriver and a hammer to chip this stuff off the walls of the pipe.

deego said:

Did you have some advice as well? Otherwise I don't see the point of your reply.

PS - It is not "Dried out soap scum, shampoo, hair and lint acumulation". I had to use a long screwdriver and a hammer to chip this stuff off the walls of the pipe.

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Yeah I know, it can't be because you want it to be hardness scale 'cuz you want to use CLR and have this problem you are scared of to go away. The point is that IMO you have the material misidentified so just maybe whatever you decide to use may not work.

I've seen such build up in traps on urinals, very hard crystalline solid. Maybe there's a clue in there.....

Before we jump to any conclusion as to what it is or what caused it, we would have to look into any chemical cleaners and sanitizing tablets/liquids used in the urinals. We might want to test the water for hardness too.

randyj,
that is pretty much limited to urinals. It's mostly urinary salts and the dissolved urinal mints. If it's a shower it's probably scum, hair and skin oil.

Did you try dropping some in vinegar to see what happens?

muratic acid

I have had to clean out a long toilet cast arm
before with some muratic acid...


you could actually watch it scour the walls clean

Of course its very nasty smelling and you need to
open some windows to vent the area.....
seal off the drain pipe with a palstic bag or smething...

we us it regulary to clean out sluggish toilets....

by simply pouring the whole gallon into the empty bowl
then covering the bowl with a plastic bag....

it totally scours out the internals of the toilet trap

then you simply flush it all down the drian...

I would guess it would do about the same thing in
the cast shower trap....

just dont leave it in there for a long period of time...
and give it plenty of air