Converting a Sunken Tiled Roman Tub area to a Drop-In Tub

[Jennifer T]

I've lurked here for years, but this is the first time I've posted. I'm an avid DIYer. I'm not afraid to do the work and the necessary research. I've done tile, laminate floor, full kitchen remodel and recently a guest bathroom remodel. On this last venture, I did hire a tile guy to do the shower surround and floor as I felt I did not have the necessary skills for it to look good or the back to complete the job. The new experience I had for the guest bathroom was roughing in the plumbing... which was completely within my ability.

We (my husband and myself... my husband does all the heavy lifting) are now working on the master bath. The problem I'm having is sunken roman tub, which has to go. I decided I would try to figure this out, and if I mess things up bad enough, I can hire a professional. I'm thinking this is another new experience within my grasp, but I have some questions. I've poured over the posts here and couldn't quite find the answers... so here goes

What I want... standard drop-in bathtub, new valve/faucet and a granite splash guard/deck

My Plan...

• remove the tile on the walls to get access to valve/faucet and re-plumb so that a new fixture is mounted on the tub deck
• remove all of the tile on walls and put in cement board/moisture barrier so that granite can be installed as a splash guard (and not floated out from the wall)
• Knock out the necessary material to create room for running the drain pipe to the existing center drain
• for the tub deck, remove whatever tile necessary with the intent of creating a solid deck (3/4” ply, cement board, etc.) and sturdy framing as necessary (will need to dry fit tub to determine if framing is needed)
• The height of the tub (Kohler Archer), appears to have the correct height that I could pour a mortar bed in the bottom of the roman tub for it to sit in. I would knock out tile to make sure the mortar bed had something to adhere to
• The windows limit the height of the tub but I think I have the 17 ½” necessary for the tub I selected. I can knock out a little material (tile first, a little concrete if necessary) in the floor if necessary to get it to fit.
• I will hire someone to install the granite

And now the questions:

• the roman tub has a center drain with a p-trap, and the new tub will have a left drain. Do I plumb the drain to the existing p-trap, or install a new p-trap directly under the new drain, removing the old p-trap and just running pipe to connect it?
• Continuation of previous question: the drain comes out 90 degrees from the tub, so there would be a 90 degree turn in the drain pipe (i.e., if you look at the diagram, the p-trap of the roman tub center drain goes toward the shower). Just wanted to ask if this was a problem.
• Do I need to concern myself with water-proofing or installing a liner or anything with the roman tub that will be hidden under the new drop-in tub and granite?
• I trust you will point out any questions I should have asked but didn't

Diagram of the bathroom:

 

[hj]

The drain SHOULD run towards the new location "somewhere", or there may be vent for the trap in the wall that you can connect to, so it would be much, much better to reposition the trap under the new tub's drain location. All you really have to do is move the drain, move the faucet, tile around the drop in location, and install the tub.

 

[Sponsor]

 

[Jennifer T]

hj, thanks for your reply... sounds like I'm not too far off base

I will position the trap under the new drain location as you stated. Vent is not in a convenient location... seems to be on the other side of the vanity. Is it OK to run from the p-trap (under new drain location) to the location of the old p-trap and put a 90 degree elbow there?

 

[hj]

Doing that can cause many possible problems, from odors to difficul, or impossible, snaking when it plugs up.

 

[Jadnashua]

The distance to the vent from the p-trap depends on the size of the pipe used. With 2", it must be within 5'.

MOrtar to support the bottom of the new tub doesn't actually have to be bonded, so you don't have to remove tile from the bottom of the old tub except to probably move the drain. With the windows, is it safe to assume you are not going to also use this as a shower?

 

[Jennifer T]

hj, not sure I understand the problem with odors, but definitely see the issue with snaking. I looked into different elbows and was wondering if my terminology was off. I see there is a short 90 degree and a long 90 degree. I've also considered that a 45 degree elbow is also possible. Would a long 90 degree elbow or the 45 degree elbow eliminate the problems?

jadnashua, thanks for clarification on the mortar bed. This will be a tub only, and will likely see little use. But with the remodel, I really want just a normal tub, so the opportunity is now.

I'm not exactly sure how to determine where all the drains are routed. It appears the vent is farther than 5' though. I'll try to figure this part out.

thanks!

 

[Jadnashua]

It is the water literally trapped in the p-trap that blocks sewer smells from entering your home. Ideally, the pipe above the trap is short. The longer it is, the more of it there is to accumulate hair, oil, soap scum, and dead skin, etc...you get the idea! A horizontal run before the trap is not a good idea. Especially one that might be 3' long.

To keep a trap from being siphoned dry by other items draining into the same drain line, they install a vent line. On a 2" pipe, the trap arm cannot exceed 5' from the p-trap for a 2" pipe before the pipe turns down to the main drainage system, otherwise, with the required slope, there may no longer be a path for air to prevent the siphoning effect.

 

[Jennifer T]

jadnashua... thanks for the explanation, that makes sense.

Will try and figure out where the closest vent is. I'm not sure there is an easy way of doing this, but I'll give it a try.

 

[Jadnashua]

The tub isn't that big, so you shouldn't have to run too far horizontally before you can run the pipe up in the wall. Code requires it to go up at least 42" or 6" above the flood plane of any other thing draining into the pipes before it can be joined into another vent, but it could, for example, run up the wall into the attic, and join a vent there.

 

[Jennifer T]

It's been a little while, but I did find the vent... I cut off the p-trap and pushed a measuring tape through until it stopped. That seemed to align with the position of the toilet (around 10'). As I pulled the measuring tape back out, I moved it around trying to feel where a vent might be positioned. Thank goodness I found one. It aligns with a clean out under the vanity, which is a little less than 4' from where I cut. I will be within the 5' from where the new drain will be positioned. Very happy about this and thought I would post

 

[Jadnashua]

Don't want to burst your bubble, but if that location is the drain for the vanity sink, it cannot be used as a vent for the tub! Would have to see the layout, depending exactly where it is, it might be a vent, but it doesn't sound like it.

 

[Jennifer T]

My bubble did burst when I realized the mistake I may have made... so I opened up the wall and found that it is a separate vent for the tub... bubble re-inflated.

I have a new problem. I knew the drywall at the floor was "bulging" and assumed it was from getting wet. I was shocked to find the way this was plumbed. It looks like an exceptionally poor job was done when the water and waste lines were run, and to work around the waste lines they ran the copper outside the studs. It would take some work, but I think I can run everything in the walls. Unless there's something here that I'm missing. Looks like a mess to me... any suggestions?

 

[Reach4]

That funny looking stuff is there because you have a slab. So they bring he copper out of the slab and do the connections above the slab. Don't let that bother you.

 

[Jennifer T]

Reach4... the problem is that they ran the copper outside the studs rather than drilling holes and running it so that the copper stay inside the walls. I can't push a vanity cabinet that has a back on it against the wall because it will hit the 1/2" copper pipe which is sticking out beyond the drywall. No other area in the house had the plumbing done this way.

 

[Jennifer T]

I forgot to mention... this is a load bearing wall

 

[Brian C]

Hi Jennifer. How did it all work out? We're thinking about doing the same thing in our 1960s home so I'm very curious to know if you're happy with the results -- and I'd love to see photos, too. Thanks in advance for any information you can share!