Tub Spout Plumbing

[ARB]

Hi,

I’m in the processing of installing new alcove tub, valve and spout. I will be reconfiguring the plumbing using pex, and I’m trying to sort out the details of plumbing the tub spout. The waterfall-style spout is attached to a “spout adapter” which has a 1/2” male threaded connector for joining it to the plumbing. My thought was to connect the valve to a drop ear elbow, and then use a brass nipple and 1/2” x 1/2" female threaded coupler to complete the connection to the spout adapter (as shown below)...

When I put the assembly together by hand (without using tools), I have noticed significant variation in how much the pieces screw into each other, which makes me think that this might be normal… Sometimes it screws in (by hand) only a few turns (less than 1/4”); sometimes it’s closer to 1/2”.

On a related note, in trying to figure out where to place the mounting block for the drop ear elbow, it also now occurs to me that I would need to “permanently” join these pieces and measure the final length of the assembly, in order to place the mounting block in the right location… (There is no “play” in how the tub spout attaches to the tub adapter, so the mounting block location is critical to having minimal gap between the escutcheon plate and the spout.

So, here are my questions:

-- Is the plumbing configuration described above a reasonable approach?

-- Is the variation I experienced when screwing the pieces together by hand “normal”? Or should I try to replace the fittings with ones that allow for deeper connections?

-- Is my thinking correct about permanently assembling the pieces and then figuring out exactly where to attach the mounting block to the studs?

Any and all advice is greatly appreciated… Thanks very much!

 

[Terry]

Normally I don't install tub spouts with PEX leading to them. On a diverter spout, it forces water up to the shower head.
If you have a diverter valve that cuts off the tub spout totally, you may be able to get away with it.
I like to run copper, and if it's a threaded spout, a male adapter off of the copper to take a pipe nipple. Or thread the entire spout piping off of nipples. I use brass for that. Even a little galvanized with drop rust in the tub with every use.

Threaded spouts have some leeway on length depending on how many turns you give it. I like to wrap a few turns with tape and then pipe dope sealant over that. Nipples come in 1/2" increments. There isn't much you can do about that. You can try to guess and be perfect, but backer board, grout and tile are not.

 

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[ARB]

Normally I don't install tub spouts with PEX leading to them. On a diverter spout, it forces water up to the shower head.
If you have a diverter valve that cuts off the tub spout totally, you may be able to get away with it.
I like to run copper, and if it's a threaded spout, a male adapter off of the copper to take a pipe nipple. Or thread the entire spout piping off of nipples. I use brass for that. Even a little galvanized with drop rust in the tub with every use.

Threaded spouts have some leeway on length depending on how many turns you give it. I like to wrap a few turns with tape and then pipe dope sealant over that. Nipples come in 1/2" increments. There isn't much you can do about that. You can try to guess and be perfect, but backer board, grout and tile are not.

Thanks for the quick reply, Terry... In this particular case there's no diverter (it's for a bath only) so I figured pex to the spout would work just as well... (True?)

To clarify the question about the variation I experienced in screwing the pieces together by hand, is it OK/normal that some pieces would only go a couple of turns before needing a wrench? (I'm probably being paranoid, but I just want to best ensure that I'm not dealing with a defective fitting before I enclose it into a wall! )

I'll also make a note to use both tape and pipe dope... Thanks!

 

[Jadnashua]

It's possible that the threads on the spout are not tapered and require a gasket (like with a water hose) to make the seal. IF that is the case, it should screw in a lot further. The coupler is likely tapered, but if that is threaded onto straight threads, it will go on much further than it would with another tapered thread. What does the spec sheet say for the spout? What about the instructions?

 

[FullySprinklered]

Iron pipe threads are not precision. They will vary in tightness per number of exposed threads, depending on how they are cut and the cut of the mating part. Lots of parts are cut by associates at the big box stores. You'll have to crank it down till it feels right and leave 3-4 threads showing.

 

[ARB]

It's possible that the threads on the spout are not tapered and require a gasket (like with a water hose) to make the seal. IF that is the case, it should screw in a lot further. The coupler is likely tapered, but if that is threaded onto straight threads, it will go on much further than it would with another tapered thread. What does the spec sheet say for the spout? What about the instructions?

Jim, you raised a point that I'm embarrassed that I completely missed! The "spout adapter" appears to have straight threads, while all the other fittings have tapered threads! Before I go any further, let me ask: Can you even connect straight male threads with tapered female threads and create an adequate seal?

To answer your question, the spec sheet and the instructions are fairly useless when it comes to installing the spout. I spoke with a technician at Signature Hardware who agreed with the configuration I described above--he said that's the way he would do it--but we didn't discuss the issue of tapered versus non-tapered threads so perhaps that was an oversight...

If it helps, below is a photo of the fittings I've been working with... You'll see on the left side the drop ear elbow, nipple, and coupler (connected together only hand-tight), I propped up the escutcheon place, and then you see the spout adapter (chrome, with the straight threads) and the spout itself which pushes into the spout adapter.

Thanks and I look forward to your thoughts!

 

[Jadnashua]

I don't have enough experience in this, but this is my guess...unless the adapter with the straight threads bottoms out, with enough pipe dope and probably PTFE tape, it will probably seal. You may have the issue where it never really tightens up well can could rotate more easily than a tight, tapered thread joint. Normally, straight threads use an end seal like on your hose. The Grohe tub/shower valve I have uses straight threads, and came with a straight/tapered adapter. I don't know how common those are or how easy it might be to find one.

 

[ARB]

I don't have enough experience in this, but this is my guess...unless the adapter with the straight threads bottoms out, with enough pipe dope and probably PTFE tape, it will probably seal. You may have the issue where it never really tightens up well can could rotate more easily than a tight, tapered thread joint. Normally, straight threads use an end seal like on your hose. The Grohe tub/shower valve I have uses straight threads, and came with a straight/tapered adapter. I don't know how common those are or how easy it might be to find one.

Thanks Jim, makes sense... I'll look forward to getting some pro opinions on this as well!