View Full Version : Master bath slight replumb

06-03-2011, 06:25 AM
I am making a minor change to my master bath. We are installing a "spa" show with many jets and shower heads, so I am increasing the size of the shower drain to 3". I want to add a 3" vent stack near the shower drain. I just wonder if it needs to be upstream or can it be slightly down stream of the flow? I think I would be no further than a couple of feet where the vent Y's into the drain. See the picture and let me know of any problems you see. I hope there aren't too many, as I am mostly reproducingwhat is already there. thanks.

06-03-2011, 06:45 AM
You cannot have that horizontal run of vent on the same plane as the drain. You need to go vertical right away.

06-03-2011, 12:00 PM
Yes, in fact that is where it should be. But if that shower actually NEEDS a 3" drain, (and ONLY a 2" vent in most cases), then the tub will be improperly installed because it would then need its own vent, due to the volume of water flowing past its connection.

06-03-2011, 02:43 PM
Maybe asking what I did was not the right way to go. I was wanting to show I had thought of a solution, but when it's wrong, you then have to bounce new ideas off of the forum and I think I am unclear as to a new solution with the replies I rec'd. I understand the horizontal and that can be fixed I think, but a new vent for the tub stumps me, because if I reused the current one coming to the shower, that would be a long horizontal run before the drain. Forgive me if I am being slow, but I want to get this right. :confused: So, how about I just show what I am dealing with and let you guys tell me the best way to solve it. I can answer any question that are not made clear on the picture. Thanks for the help.

06-04-2011, 01:14 PM
Also, I only have a 2x4 wall, so doing the 3" vent would require cutting the top plates completely out and depending how far downstream you suggest I can go from the shower, I might not be able to get to the top plates fro the attic to brace the cut wall. Can I use the 2" vent that is there and just add another 2" through the roof and Y these into a 3"? TIA

06-04-2011, 01:58 PM
The tub is getting pretty close, if not past, the length you can go without its own vent, and you cannot extend it to the right where the old drain was to use it as a vent. HOW you do the shower is somewhat immaterial as long as you vent it properly. You probably only need one 2" vent, if done properly, but if you do use two, you should be able to tie them together and just exit the roof with a 2" vent, unless you already have a 3" hole in the roof.

Tom Sawyer
06-04-2011, 02:00 PM
from what I can see the tub is going to need it's own vent. I believe the distance is too far. an 1 1/2 vent will carry a bath group.

06-04-2011, 03:35 PM
Thanks so much for the replies and helping a DIYer work through the process...
I have since removed the shower and see that the vent is downstream of the shower drain. So HJ, you say if it's vented properly, 2" would be ok. Where should the 2" vent hit the 3" shower drain line for it to be enough? (BTW, I have already purchased the 3" drain line, so regardless of necessity, that's what I'll be using. granted, I probably won't need it, but I don't want a wading pool under any circumstances and I have 2 heads and 4 body sprays that might all be pumping at the same time, depending on how I set-up the diverters). And can someone explain the reason the horizontal run is bad in the first pic? Is that because it's upstream of the T/Y? because the way the shower is plumbed now, there is a horizontal downstream of the drain? The reason I ask, other than basic knowledge and clarification, is I could do a vent to the right of the tub drain, but it would have a horizontal run to tie in. If I do this, would I need to tie in downstream of the drain? And is there a limit to vent runs in this position? TIA again.

06-04-2011, 06:43 PM
do you have the 3" drain for the shower yet? i dont think you can make a 3" p-trap fit in the floor, there isnt enough depth. how are you getting the 3" pipe to the shower? not through the joists i hope. the tub is already past the distance for venting. its usually 5 feet for 1-1/2 drain and 6 feet for a 2" drain. you dont really need a 3" vent there unless you dont already have one in the house somewhere.

06-04-2011, 09:41 PM
5 feet for 1-1/2 drain and 6 feet for a 2" drain.
Distance for the vents is given in UPC table 10.1
1-1/2" pipe => 42" or 3-1/2 feet
2" pipe => 60" or 5 feet
3" pipe => 72" or 6 feet
4" pipe => 120" or 10 feet

I think the 3" Drain is way over kill for a tub,,, A 2" pipe will move alot of water

06-05-2011, 12:29 PM
Well, for one thing, this is NOT a "slight bath replumb", and we have a hard time correlating your description of what you want to do with what has to be done. IF WE were actually there, we could decide how to do it very quickly, AND do it, but it is difficult to describe it in a way that we could be sure that you would actually do it like that.

06-05-2011, 04:22 PM
My apologies, I thought it was a "slight bath replumb". Did it turn into something else when it was discovered that the tub drain was well over allowable limits? I figured it had been done properly and I was just moving some things a little and converting the vent to 3".

With the comments so far, I am convinced that I can go with a 2" drain (just to make 100% sure, my valve can generate 8.9 GPM and I am thinking of adding another, so max would be ~20GPM), so I will return the 3" and go with 2".

I have attached a top view of the bathroom as I see things now. So, is it better/required to vent downstream (I say this instead of before/after to avoid confusion), to avoid horizontal run upstream of drain? I guess I will see about adding a vent to the other side of the bathroom to tie into the tub drain as I have shown in the drawing.

06-05-2011, 04:50 PM
that looks good except i dont see a vent for the tub. for the shower i would head right for the shower and put a tee or a wye in the line and roll it up at least 45 degrees to take off for the vent. it only needs to be 1-1/2 for the vent.

Tom Sawyer
06-05-2011, 05:48 PM
Yep, it's way past the slight remodel stage indeed. The venting is going to be the issue here. Stay within code requirements for trap to vent distances and remember that vents need to rise vertically to a point 6" above the flood level rim of the highest fixture served ( the lav) before they can run horizontally.

06-05-2011, 05:56 PM
20gpm might push the limits of a 2" drain. The original tub probably had a 1.5" drain (although the pipe might be larger). A 'standard' shower requires a 2" drain, and is generally sufficient for most, even with some body sprays. What may be a bigger issue is what kind of industrial water heater are you planning if you go that way? And, have you got big enough supply lines?

06-05-2011, 07:51 PM
Thank one and all for the help.

DanTee: The vent for the tub is at the bottom of the graphic (right in the room). Glad to hear 1 1/2" will work, because I think that the wall it would be going in is right over a joist. I have to see how much wall is left on the side of the joist.

jadnashua: 20GPM is probably a pipe dream ;) , it would probably never happen. I am contemplating upgrading to a tankless, from a 50 gal., that delivers 9.5GPM max with a solar preheater, so max is more achievable and mixing with cold would, yield more than the 9.5, right. What I'm saying is I want everything going behind the tile to be as future proof as it can be...I think 2" drain will be fine. I was going to use 3/4 to get to the shower and then step down to 1/2 to branch to each valve/diverter.

Tom: thanks for the code. Let me show my ignorance by asking for clarification. It sounds like what you are saying makes perfect sense for a lav that backs up to a wall. I can envision the stack going up in the wall 6" then running horizontal, if needed, but what about that shower that's already in my floor? I'm seeing horizontal runs before they tie in? Is this just 100% wrong, or right in certain circumstances. Or is it OK if the vent has slight slope downward (as in not level, but pitched toward the T/Y, etc.).

Thanks again for all the help. I'll beat this thing yet.:confused:

Tom Sawyer
06-06-2011, 03:29 AM
100% wrong yes. You must rise vertical or at a 45 degree angle. Flat vents are not allowed. And it makes sense because a flat vent will eventually fill with crud and plug up. Unless the vent can be washed from an upstream fixture ( wet vent)

06-06-2011, 06:07 AM
The limit on the shower drain will be the drain itself. If it has few, or small, openings it will not drain properly no matter what size pipe it is connected to. Either tub location appears to be too far without its own vent, and the shower vent, as shown, is horizontal which is also not permitted.

06-10-2011, 02:14 PM
OK, if I can get these vents close enough to the drain lines to get them coming in at 45*, would this work?

What kind of slope is required in the drain lines?

Thanks for helping.

06-19-2011, 07:56 PM
OK, I have got the drain taken care of. Now I have a question about plumbing my supplies to the shower. I am planning on finding the copper supply going to the master bath and converting to PEX. I am thinking of at least 3/4 PEX to a minibloc that steps down to 1/2 PEX for the fixtures, but the minibloc has 3/4 inlet and 3/4 outlet. I am planning on using the outlet to supply the shower to get maximum flow. My valves are 1/2 copper, so stepping down 3/4 PEX to 1/2 copper into the valves and fixtures, but planning on going back 3/4 PEX between valves and fixtures, again to maximize flow. Does this sound OK? Also, is there a 3/4 PEX T that T's to copper? Street 1/2" copper branch coming off 3/4 PEX thru would be great, so i can make my balancing loops as "thin" as possible, because I am working with recessed bocy sprays on an outside wall. I am using 2" foam rated at R-10 and am trying to keep as much of this in place as possible, by reducing the amount I have to cut into it to allow for the plumbing. TIA!

06-20-2011, 06:27 AM
You are not helping yourself by using "oversized" PEX, because, due to the thicker walls for plastic pipes, a 3/4" PEX line is not much larger than a 1/2" copper one, and 1/2" PEX is "ridiculous".

06-20-2011, 07:30 PM
Again, maybe I didn't present this right...

1) would using a minibloc 13350 as described above and shown here still serve the purpose of pressure equalization with the shower actually being the outlet?
2) does anyone know of 3/4PEX-3/4PEX-1/2 sweat adapter, so I can attach my body sprays using this right in my equalizing loop to minimize the depth behind my body spray?

06-20-2011, 07:58 PM
I take that back, I don't need a sweat for the T "leg", but a piple thread (nipple is what's supposed to screw into body spray), so need 3/4pex>3/4pex>1/2MPT T or settle for elbow I guess...