3 handle valve to single handle valve question.

[cdubya]

I have a 3 handle valve in a tiled tub/shower and want to update to a single handle valve. The existing drop from valve to tub spout is only about 5" and Delta calls for an 8" drop. If I move the valve up to create the proper drop, the adapter plate won't cover the 3 handle holes in the tile. Is there a way to compensate for the less than minimum drop that is reliable/legit?

[Dunbar Plumbing]

I've set countless valves without that minimum without error or callback, but I prefer to follow mfg. specs whenever possible.


The piping between the tub spout and the showerhead must be copper piping.

[hj]

That 6" dimension was decided upon by an engineer who had absolutely no idea why it had to be that way. Maybe because he read some book published in 1940 that specified that dimension. If the trim ring on the new valve does not hit the spout, do it the way you have to.

[TedL]

Just guessing, but if you're using something based on Delta's "universal" valve, that spec may be to cover any possible trim they may intoduce at some time unknown, which could include trims that need that much space to avoid the handle trim meeting the tub spout.

[cdubya]

Thanks for the comments. Delta said the 8" minimum drop is so water won't back up and dribble out the shower head when filling the tub. If the 5" drop isn't enough, I've wasted time & money on a new valve. The old tile can't be matched to patch existing holes if I move the single handle valve up. What do I do if I get the dribble on the 5" drop?

[kingsotall]

You'll have an understanding of why it does that and maybe could possibly live with it. Some people call these things giving a house character.

[hj]

You might get a "dribble" if the pipe were LONGER than 8", but almost impossible when it is less. The dribble is caused by back pressure and the longer, or smaller diameter, the drop the more back pressure is created.

[cdubya]

Apparently, Delta agrees the drop can be too much. They advise the drop from valve to spout be 8"-18" to avoid "shower-rise". First, I've got to figure out if the cover plate will fit above the new spout and still cover the existing holes. Even with your encouraging comments, it feels like a leap of faith with the existing drop being so far outside the recommended range.

[Terry]

If the tub spout doesn't hit the "pie pan" you should be fine.

It's a common replacement for us plumbers.

[hj]

You are placing "way, way" too much faith in the intelligence of an engineer. They deal in theory which they seldom test. We deal in actuality which we test daily.

[cdubya]

I like your conviction. I need to check for the clearance issue and go from there.