At least I think it may be an issue at the mixer valve. This is in a multi-floor condo in south Florida where calcium and lime can also be an issue.

When hot supply is opened both the shower head outlet and the tub outlet provide reasonable water pressure. However, when the handle is turned all the way to cold, the water pressure is unreasonably weak. It's still supplying some water, but not enough to meet a pressure use standard.

One obvious possibility is the cold water that supplies the mixer valve is providing limited pressure (due to CLR buildup or for some other reason). However, the cold supplies to the adjacent toilet and sink seem to have normal pressure outputs. And all other fixtures throughout the unit have good pressure.

I'm really hoping that I don't have to open the tile and wall apart to diagnose/fix this issue. What would be the best progression to diagnose this cold water pressure issue in the shower?

You can see the image below. Thanks.

[db.tt]

The problem is in the valve. Do you have screw driver Stops on each side of the valve? You must shut off the to water to the valve fix it.

Thanks. I thought of that, but I thought the stops were more on the hot side to prevent scalding. My second problem is removing the handle. Whenever I've done this before there is a set screw underneath and this particular one is giving me fits. Is there a standard size Allen wrench/set screw for most handles attachments?

Ok, I have progressed with the diagnosis, but still have questions. Very much a product of lack of extensive experience, I realized that it was not necessary to remove the allen screw for the handle. Instead, the wider throat of the handle extension needed to be unscrewed from the mixer valve. Ok, good, now I can view inside. Picture link below to show inside.

[db.tt]

As was mentioned the screw stops are present, but access to the cold side is behind the tile. However, after a closer look, the screw stop for the cold side shows about 3 1/2 threads exposed, approximately matching the hot side screw stop position.

Should I remove tile pieces in front of the cold stop screw to open the screw stop more? Or does the pic show it's open enough (and therefore not the problem)? If I do remove some of the tile to gain access, what is the best tool for this delicate situation? I don't have my full complements of tools in Florida at the moment, so I need to use what I have or buy it. I do have a tile drill bit, the one that looks like an arrowhead. I suppose I could use that to hone out a hole big enough for a screwdriver, but is there a better way?

Any other thoughts or possible issues and/or solutions?


**EDIT with added clarification**

After submitting this post, I inspected the two holes (vertical slits) on each side of the mixer valve. I gently inserted a small headed screwdriver into each slit and found there was something inside the cold side, but not inside the hot side opening. So I took a close-up and it can be seen here -

[db.tt]

In the close up (you can expand with Dropbox's '+' button), there looks to be some metal inside the cold slit opening. This has to connected to the stop screw design, correct? It also probably means, since initial installation the cold water supply to this shower has always had cold supply pressure issues.

Would the screw stop open/close a mechanism in the slit opening that I am currently observing or would the screw just "plug" the space immediately below it (by screwing down into the opening)?

I suppose the best answer right now is to gain access to the cold screw stop and open it more to test. So, what is the best tool to remove the needed tile without causing damage? Thanks.



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Can you take a needle nose plier to turn being careful not to ruin the threads?

I would not remove the entire tile to access. You can bore a small hole where the screw slot is with a "tile/glass/stone" cutter (they work amazingly well in tile). The hole doesn't have to be as big as the screw head, just enough to fit your screwdriver to turn it. Your hole will be close to the edge so you'll have to get creative centering it. Use a piece of wood and drill a hole with a regular drill bit the size of your tile cutting drill bit and use it as a guide for the new hole, then have someone hold the wood as you drill through that hole with your new toy.

I use these specialty drill bits all the time to drill holes for anchors in showers and kitchen tiles on the wall for microwaves.

[images.homedepot-static.com]

Thanks. That makes sense. However, there is an added problem in this situation. The top of the screw head is almost touching the back of the tile. I'm guessing the tile installer ran into this screw head in the fully open position and rather than cut the appropriate opening in the tile, he just turned the screw down enough to get his tile flat. So, it looks like I need to make the opening big enough for the full diameter of the screw head.

I like your idea for using a wood jig as a guide. I have a single "arrowhead" tile drill bit, like this one

[images.homedepot-static.com]

I wonder if I should buy the set of tile bits so I could progressively expand the hole? I don't have a Dremel with me, but if I had to, for a one-use case, I could buy a similar tool at harbor freight. Generally, I like to invest in the best tool to last, but I'm just helping family in this specific predicament.



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"Drill, baby, drill". If you make the drilling jig, you can use the same bit to drill multiple holes. There is a pointiness to your bits so you may have to do that as you won't be able to drill the full "width" of your bit as the pointed end will hit the screwhead.

Do you need to loosen the retaining (?) nut I see in your picture before you screw/unscrew the screwhead in question once you have access? I'm not familiar with this and hope someone can chime in.

I had second thoughts about creating 2 or more holes with the solid tile bit/s. In plenty of other applications, I used hole saws before and thought it was probably worth the extra money. It can be seen here -

[images.homedepot-static.com]

I choose a 1" diameter hole saw. It was slightly larger (and more expensive) than what was required to access the screw stop because I wanted to have more surface contact vs. less on the face of the tile. With half of the surface area already removed my logic was to minimize any creep. I started the saw cut at 45* and pivoted to 90* to make the following opening -

[db.tt]

Once I had access to the screw stop, I was able to turn to its correct position. Now, both supply sides provide good pressure. Problem solved!

Thanks to all suggestions. They helped a lot!



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good job...



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