Shower head drips, even with diverter open

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sherrardb

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i have spent a lot of time lurking around this forum during the course of a major kitchen and bath remodel, but this is my first post, so please forgive any faux pas.

i have a problem which i think i understand, but don't know how to remedy. the plumber came this week to install the shower valves and trim. in case it helps, this is the delta lockwood series with pressure balanced valve and a pull-down diverter on the end of the tub spout.

here's the problem: when the mix control handle is in certain positions, basically anywhere in the "middle range", i get water flowing from the shower head. and the closer it is to dead center, ie an equal mix of hot and cold, the higher the flow is from the shower head. and the flow decreases accordingly as you swing toward either of the extremes. there is never enough water to, say, take a shower with, but at its greatest point, it is well more than a simple drip.

based on the remedial troubleshooting that i did to gather the above information, i deduced that it is simply an issue of having more water flowing from the valve than the spout can handle and, therefore, since there is no positive shower shutoff, it finds the path of least resistance, which is out of the shower head. to further confirm this theory, and to make sure that there wasn't simply a blockage in the spout, i screwed the spout off and ran through all of the same exercises as i had before. and guess what? i get a strong stream of water streaming out of the adapter that the spout screws onto, but never any water from the shower head. so it seems pretty clear (although i definitely could have missed something) that at the higher flow rates, there is enough restriction provided by the natural internal design of the spout that water is being forced out of the shower head.

so here are my questions:

1) have i overlooked something, or am i just way off base?

2) is this something people have seen before?

3) if this diagnosis is correct, what is there to be done about it?

thanks in advance for your time and patience , and for any assistance you can provide.

ps--for the record, i'm not a licensed anything, just a capable DIYer. i dabble in plumbing, electrical, carpentry, and general troubleshooting and problem solving.
 

Jimbo

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It is related to the installation, and possibly to your system water pressure. You are correct that the spout allows MOST of the water to flow out there, and the dynamic pressure at the inlet to the spout usually is low enough that no water rises all the way to the shower head. But if system pressure is on the high side, or if the flow to the spout is restricted, then you get the drips.

VERY COMMON PROBLEM: The piping from the valve to the spout must be full size....i.e. it must be 1/2" ID copper, or 1/2" ID brass or galv. pipe. The install instructions for your valve specifically state that PEX tubing must NOT be used. ( ID too small).


So, check your house water pressure, and see what kind of tubing was used to install your valve.

delta-tub-spout-install.jpg
 
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hj

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flow

The problem is not that there is more water going to the spout than it can handle, but rather more water is trying to flow down the pipe AT THE VALVE, than the pipe can handle therefore the excess goes up the pipe and out of the shower head. There is seldom any reason for this to happen except if someone used plastic pipe between the valve and the spout OR the valve was installed upside down.
 

sherrardb

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VERY COMMON PROBLEM: The piping from the valve to the spout must be full size....i.e. it must be 1/2" ID copper, or 1/2" ID brass or galv. pipe. The install instructions for your valve specifically state that PEX tubing must NOT be used. ( ID too small).

well i can definitely say that pex was used from the bottom side of the valve to the spout. there is a piece of pex, then a section of cooper with a gradual ninety-degree bend in it that had a bullet-shaped point on the sealed end until they trimmed it for the final installation.


So, check your house water pressure, and see what kind of tubing was used to install your valve.

do you know where i could find/buy/make the device used to take a quantitative measure of the system water pressure?

as much as i enjoy the good forceful flow at this house, as compared to the last one, if pressure reduction is going to keep me from having to tear into the walls, then i'll have to seriously consider it. even though the upstairs bathroom has been closed in for a while now, the downstairs tub backs up to a closet and i just got through closing it in with drywall. i haven't mudded yet, so, depending on the other options, i may just pull that back drywall down to get at the plumbing.

thanks a bunch
 

sherrardb

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Or, if you have extremely high water pressure...

i would say it is significantly higher than my previous residence, but that's not very quantitative is it? i don't remember seeing a pressure regulator, but i may have overlooked it. i'll try to check for sure the next time i'm over there.

i was waiting for someone to reply on where to find a water pressure gauge, but then i remembered that mr. google is my friend. so i guess i'll be checking the home stores tomorrow, and possibly the plumbing supply house monday.

i'll also try to remember to place a call monday to find out what the expected static water pressure range is for my area.

thanks
 

sherrardb

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The problem is not that there is more water going to the spout than it can handle, but rather more water is trying to flow down the pipe AT THE VALVE, than the pipe can handle therefore the excess goes up the pipe and out of the shower head. There is seldom any reason for this to happen except if someone used plastic pipe between the valve and the spout OR the valve was installed upside down.

yes, there is unfortunately a pex line from the valve to the spout, but i don't quite understand how this alone would explain the problem, given that it stops happening when the spout is removed. are you saying that the pex line is the sole source of the problem, or that it, combined with possible pressure issues, are at fault?

thanks
 

Jadnashua

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The instructions for many valves specifically say NOT to use pex to the spout. The combination of the restrictions of the spout and the interior diameter of pex very well could be the source of the problem. Often, the manufacturers actually do know what they are talking about...following them really helps!
 

Redwood

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The PEX to the spout is well a well known cause of water diverting to the showerhead...
 

hj

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restriction

The diverter spout, by its design, has a certain amount of restricion, but by it ]self it is not a problem. Adding the immense restriction caused by the PEX is what causes your problem. Some might say that the PEX i.d. is not that much less than copper tubing, which is true, but since the reduction in area occurs on the outer part of the diameter, the reduction in area is disproportionately greater.
 

Jimbo

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A simple pressure gauge is about $10 at any hardware or home store.

PEX is a well known issue, which is why the manufacturers specifically call it out in their instructions. Pressure above the maximum allowed 80 PSI will aggravate the situation, since the basic issue is dynamic pressure at specific points in the flow system.

moen-tub-spout-install.jpg
 
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sherrardb

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thanks a bunch everyone. didn't make it to get the pressure gauge today, but i plan on doing that, as well as calling the plumbing contractor tomorrow to try and determine the best path for resolution, i.e. the one that strikes the best balance between correctness and inconvenience to me. while it is clear that the installer should have known this, the fact is that rectifying this "the right way" is going to be a big headache, give that this doesn't sound like the kind of thing that can be done through a reasonable-sized access hole. but then again, adding a pressure regulator might not be a gimmie either, given that the house is slab-on-grade, and the main line and the shutoff are only stubbed a few inches out of the slab. not much margin for error there.

so we'll see tomorrow. and thanks again for all of the guidance.
 

hj

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pressure

I cannot remember ever seeing an installation where excessive pressure caused your problem, and we have pressures up to 140 psi in some areas without it happening.
 

sherrardb

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Alright! Did you put a thermal expansion tank on the water heater inlet?

i didn't. but after seeing some gradual increase in pressure over a period of time, it is high up on my list. i'm guessing that one won't be too hard to tackle. any magic to selecting or installing one of those? do you have to size them according to certain system parameters such as static water pressure, water heater volume or temperature setting?
 
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