Cast iron shower drain--reuse or replace?

[ShaunS]

Hello, newbie here. My shower pan was leaking so we've embarked on a complete bathroom remodel (tearing out the shower, who not everything?). After pulling up the pan I found this:

I've had two plumbers come take a look. The first one says tear it out back to the T and replace with PVC--$1900. The second says it looks fine, just get a new drain assembly and you're good. I'd like to get a 3rd opinion, but thought I'd ask online too, so here I am. The first plumber looked at it for about 5 seconds before saying it needed to come out, and he seemed a lot sharper than the other guy. The other guy said it's not falling apart and the trap's holding water, so keep using it.

Thoughts?

My gut says rip it out while it's exposed and "do it right".

 

[Terry]

I would start a new shower with a new drain. I would not reuse what you have there.
Maybe the p-trap is okay, but if you can change it out, why not?

 

[Sponsor]

 

[ShaunS]

I would start a new shower with a new drain. I would not reuse what you have there.
Maybe the p-trap is okay, but if you can change it out, why not?

Thanks. Once I'm opening on the slab, why not is right!

 

[Jadnashua]

Code calls for the waterproofing layer to be sloped to the drain...the tile is not the waterproofing layer, so the location (height) of the existing drain may or may not be correct. THen, you need to determine whether you're going to build a conventional shower with a liner and a clamping drain, or what I prefer, one with a surface applied membrane. The reason is, each one takes a different type of shower drain, and each one needs different elevation.

One thing to pay particular attention to is the ensure that the vertical riser from the trap is perfectly plumb. Once you tear things up, also try to get the drain as close to the middle of the shower as possible.

 

[ShaunS]

Thanks for the advice. I had hoped to build a Kerdi shower, but that doesn't seem possible without busting this out at least to some degree.

 

[Beaglebuddy]

If you are gonna cut it out might as well replace the p trap as well if it's made from cast iron because they can rot out or get full of rust and snag hair and scum.

 

[Jadnashua]

Schluter does make a conversion drain, but if you really don't know the state of repair of what's underneath, it's probably not a great idea to use it. To use that drain adapter, you'd have buff off all of the rust on the base part so you could get a proper seal AND, reuse the bolts that held the top part on (or find some that are the same size) to attach the adapter.

 

[ShaunS]

Schluter does make a conversion drain, but if you really don't know the state of repair of what's underneath, it's probably not a great idea to use it. To use that drain adapter, you'd have buff off all of the rust on the base part so you could get a proper seal AND, reuse the bolts that held the top part on (or find some that are the same size) to attach the adapter.

Unless there's a different part, their adapter won't work. It only has 4-bolt patterns and I have 3 bolts. It's sealing diameter is larger than my flange. And the drain is still 2" outlet and my cast iron is 1.5". I don't think it'd work at all.

 

[Plumber69]

Jack the ptrap out and camera the rest. Cast is awsome but 50 years later has its flaws

 

[ShaunS]

As a follow up to this, is this a feasible job to do myself? The plumber offered to lower the price if I jackhammer myself, so now I'm wondering if I can just do it all. I'm a reasonably accomplished DIYer, but haven't done a ton of plumbing.

 

[Jadnashua]

FWIW, at least in the USA, code requires a 2" drain for a shower, so if that part is 1.5", technically, you'd have to tear out enough pipe until you found where it is at least 2". Now, will it work? Probably, but it might not pass code...depends on how accommodating the inspector is. Now's the best time to fix it.

 

[ShaunS]

FWIW, at least in the USA, code requires a 2" drain for a shower, so if that part is 1.5", technically, you'd have to tear out enough pipe until you found where it is at least 2". Now, will it work? Probably, but it might not pass code...depends on how accommodating the inspector is. Now's the best time to fix it.

Thanks. Now that removing it seems like a go, my mind has wandered to what possibilities this could open up for changing up (enlarging) the bathroom. What is the feasibility for swapping the shower and toilet drains? I know a toilet should be 4" and a shower 2". So reducing the toilet down to a 2" seems straightforward, but what about enlarging the shower to a 4"? Is it all going to depend on what the connections look like once it's dug up?

 

[Reach4]

Thanks. Now that removing it seems like a go, my mind has wandered to what possibilities this could open up for changing up (enlarging) the bathroom. What is the feasibility for swapping the shower and toilet drains? I know a toilet should be 4" and a shower 2". So reducing the toilet down to a 2" seems straightforward, but what about enlarging the shower to a 4"? Is it all going to depend on what the connections look like once it's dug up?

3-inch is enough for a toilet. You are not allowed to have a bigger drain pipe pass water to a smaller pipe unless there is a sewage pump in between.

 

[ShaunS]

3-inch is enough for a toilet. You are not allowed to have a bigger drain pipe pass water to a smaller pipe unless there is a sewage pump in between.

Thanks for info. My question is still kind of the same. Should it be straightforward to take out the 1.5" shower drain and put in a 3" toilet drain? Or just impossible to tell until it's dug up?

 

[Reach4]

Thanks for info. My question is still kind of the same. Should it be straightforward to take out the 1.5" shower drain and put in a 3" toilet drain? Or just impossible to tell until it's dug up?

I just pointed out a a couple of things that I thought might be useful in early thinking about the project.

I am not a plumber. It would not be straightforward for me. If I were, I would need to see what is below the concrete to know how involved it would be. What is straightforward could mean different things to different people. Once enough concrete is removed and dirt dug, I suspect it becomes straightforward if you do not have high groundwater.

 

[ShaunS]

I just pointed out a a couple of things that I thought might be useful in early thinking about the project.

I am not a plumber. It would not be straightforward for me. If I were, I would need to see what is below the concrete to know how involved it would be. What is straightforward could mean different things to different people. Once enough concrete is removed and dirt dug, I suspect it becomes straightforward if you do not have high groundwater.

Thanks. It does sound like we won't know until opening up the concrete. Good news I suppose is that I'm going to replace it anyway, so we can make a game-time decision once it's opened whether to go with the enlarged bathroom idea.

 

[Jadnashua]

While it is possible to trace the pipes without tearing up the slab, since you have to do that anyways, wait until you have, then make your best call. You also need to keep in mind the required vent lines as well as the drainage lines. There are maximum runs based on the size of the pipe for vents: on a 2" pipe, you must vent it within 5', so keep that in mind.

 

[ShaunS]

While it is possible to trace the pipes without tearing up the slab, since you have to do that anyways, wait until you have, then make your best call. You also need to keep in mind the required vent lines as well as the drainage lines. There are maximum runs based on the size of the pipe for vents: on a 2" pipe, you must vent it within 5', so keep that in mind.

What about the 3-4" toilet? It will be further away from the vents. The "new" 2" shower will be within a foot or two or the vent line.

 

[Jadnashua]

If I read it correctly, you have 6' for a 3" pipe, and 10' for a 4" or larger pipe from the trap to the vent maximum.

 

[Cool Blue Harley]

Because the water closet and similar integrally trapped fixtures function as self-siphonage fixtures, their traps are an S-type. In this case, the trap arm length is calculated along the developed length of the piping from the top of the closet flange to the inner edge of the vent. A water closet trap arm is limited to 6 feet whether it is 3 inches in diameter or 4 inches.