I am planning a master bath remodel. Part of the plan is to swap the locations of the tub and shower and I want to make sure that I'm not setting myself up for problems with the plumbing, particularly the drains.

Currently we have a small 34"x44" shower on the left and a large, elevated garden tub on the right. We are installing a larger 54" x 42" shower on the right and a freestanding tub on the left:



Current layout

New layout

My thinking is swapping tub for shower and relocating the drains accordingly is probably not an issue, but before I spend several thousand dollars on fixtures I wanted to get some confirmation.

The drain plumbing is laid out in yellow below. The entire master shares one plumbing vent for the tub, shower, toilet & 2 sinks.The master is at the farthest point of the house away from the septic system. I can share pictures of the system from the crawl space, but it's hard to get a good complete picture.

Any concerns with swapping the shower & tub that I should be aware of?

Thanks

Drain layout

 

I'll offer a suggestion for consideration.

Many years ago I did a complete remodel of our bathroom, similar set up, tub and small shower. We ditched the tub and built a huge walk in shower, something that I had the pleasure of using many times at airports when I did international travel.

That shower is approx 4'x8' and have never regretted the decision. Those big tubs are a complete waste of space, we have a regular tub in another bathroom but I don't think anybody has used it for as long as we have lived here, 15 years.

 

The drain lines will likely be an issue. Showers are required to have a minimum of 2" while tubs only need 1 1/2" so you likely will have to replace the drain piping in the floor.

 

My wife loves the tub, so it needs to stay. :-D

The drains will be relocated, so a good portion was going to be replaced anyway. It's not a long way to the main, large drain line, so that shouldn't be an issue. It's in a crawl space, so access is OK.

I assume having the new tub connect to the 2" that's already there for the old shower is OK, but the new shower will need 2" all the way to the main line, correct?

 

Yes, the tub can be connected to 2" piping. The code is merely the minimum allowable. I assume your plumber will also inspect the vent locations and make sure they are not located too far away from your fixture's new locations.

 

That's one of reasons for posting here. I hope to DIY the plumbing and I've had good luck getting guidance here for staying within code and best practices here.

There is one vent (that I can see) for the entire bathroom. My thinking is that the new tub drain will move 2'-3' away from the vent relative to the old shower location and the new shower location will be closer to the vent by maybe a foot relative to the old tub location.

I'd like some input if this seems reasonable or not. I can get more detailed measurements or supply more pics if that helps.

 

Figuring for the vent depends on the pipe length. So, you really can't figure until you measure the pipe lengths between everything depending on how the piping is run.

Here is a webpage that talks about vent distances and how many fixtures can be on a vent. For example on a 1 1/2" pipe the vent must be within 3 1/2' while the vent can be 5' away on a 2" line. It looks like your exceeding that already with the sink unless there is a vent in that wall. For comparison my master bath has four vents that tie together in the attic.

 

Thanks, that helps. I'll take a look at that site.

I had a hunch this set up might not be up to snuff. There may be a vent in the wall where the sinks are, which would improve things. Seems likely, actually. There's only one pipe through the roof and it's above where the sinks are. I suppose the one on the outside wall may pass through the attic and join one that goes up from the sinks. I'd have to get into the attic to check.

 

OK, here's my new plan. The red is new 2" pipe, the yellow is existing 2" and the green is the existing main larger (4"?) that starts at the toilet. The yellow circle is a 1.5" vent.



The tub drain will be close to the old shower drain, it might add a foot of length. The new shower drain will be closer to that vent and will attach to the old shower 2" pipe instead of where the old tub connected into the old sink 1.5".

Any thoughts or concerns with this plan?

 

I don't see any issue with your proposed changes. Since it's a crawlspace, it's easy enough to upsize some of the pipe and not worry about drilling floor joists and such.

The vanity needs to be vented as well, but I assume that's already in place.

 

I assume that the sinks are vented through that wall, but I haven't confirmed yet. I don't imagine they'd work well if they were not.

 

Have you been in the attic to see what access you have to run the new vent line? It might be difficult or impossible with the vaulted ceiling. If you can't access the attic you can cut the sheetrock and run it straight up and out through the roof.

 

Sorry, what new vent are you thinking I will need? For the new shower?

I have been in the attic before, but not to look at this area closely. I think access to the vaulted ceiling area is very limited.

 

I am sorry, I thought the vent you indicated was going to be new, not existing.