I have a single handle shower in my basement that is too cold in the winter. I only need a small adjustment, but I don't know if it's even possible.

The "hot water stop" appears to be already set to max. The following image is from the manual:

shower manual

photo of hot water stop setting

My current setting is all the way counter-clockwise. I tried turning it clockwise for science, and it makes it colder.

What is the most proper solution, given standard plumbing technique and so on?

1) I see that there are screw-valve things to either side of the handle base. They both appear to be turned fully counter-clockwise (There is strong resistance in that direction). Someone implied that it's okay to try tightening that. Tightening the cold water screw three half turns appears to have warmed the shower some (hard to say because it varies with weather and such). Regardless, shouldn't this be unnecessary? I wonder if something else is not working properly?

2) Turn up the water heater, which is at factory default. Note that I don't feel this should be necessary, as water coming from the upstairs shower is warm enough, and the sinks can get way too hot. Plus I worry about the dishwasher etching my dishes.

3) Something else?

There are no valves outside the shower that could restrict the water in, (hot or cold) besides the main cold and water heater input valve. The water goes from the basement utility room, to behind the shower, then split off to the bathroom sink and end there.

Both pipes to the bathroom, when unused for houses, feel about room temp. They don't rest against any surfaces that would cool them down.

I have city water. The plumbing is of unknown age. The house is from the early 60's. The pipes are all copper. There is about 25ft of pipe from where it enters the house to the water heater tank. Then another 20ft to the back of the shower, the last 10 feet or so are 1/2".

UPDATE: The shower handle, going from "Off" position to "Hot" appears to ramp-up in a non-uniform matter. So as I start turning it, it goes to something like 20% warm, 40%, 60%, but then goes back down to 40%, then 60%, 80%, 100%. It does this regardless of the screw-valve's being fully opened or not.
Is this a faulty cartridge, or something else? ...And would that be the cause of the shower not getting warm enough without restricting the cold valve?

  • What size is the hot water piping into the shower? Is it kinked anywhere? How old is the plumbing? And joints that look like "crap"? There aren't ANY valves between it and the water heater? Are you on well water or city water? Might want to (since you are in there already) taking apart the valve and make sure there isn't any debris inside. Has the cartridge been replaced? If so, maybe check to get an OEM cartridge vs. a big box store brand because I have seen a clear difference between all plastic and a more solid, heavy metal unit.
    – noybman
    Commented Feb 7, 2018 at 3:24
  • 1
    @jsotola - Well you assumed the worst in me. My apologies for not making it more clear. '"They both appear to be turned fully counter-clockwise"', as in: I don't think I can turn them any further. I'm not visually ascribing that! How could I? Perhaps there is no "limit" and there is just resistance. I wasn't sure if I would end up stripping threads or breaking something. I think some hand-turned valves do not like being rotated too far in either direction (needle?). I don't know, I'm not a plumber.
    – Bort
    Commented Feb 7, 2018 at 4:28
  • @jsotola - As for "Perhaps tightening...", again, I'm not a plumber. I interpret your comment as snarky, in that I should have tried it to begin with. However for all I know, I should not be messing with those screws. Perhaps they don't even do what I think. Perhaps I'm just an EE who wants to learn how to DIY without damaging their house any further. This is not an area I can afford too many assumptions in. I searched around with my limited plumbing lexicon and didn't find what I needed. Anyways, I tried it now that someone implied it wasn't a bad idea, and I have updated my question.
    – Bort
    Commented Feb 7, 2018 at 4:35
  • 1
    @Bort, I am sorry, i was being rather snarky, as you have observed. i guess that i have read too many posts where people ask a ton of questions without trying the basics first. ... if I was troubleshooting your problem, i would first find out which side is hot by touching it. ... then i would run cold water and turn the adjustment to both extremes, just to find out the range of adjustment available. then do the same with the hot side. ... i would then turn both to max. ... i would then try to figure out if the main control valve rotates all the way to hot, or if it is being blocked
    – jsotola
    Commented Feb 7, 2018 at 6:31
  • 1
    You don't need a caliper to measure pipe size, pipes are either 1/4, 3/8, 1/2 or 3/4 trade size (which is an approximation of what the inside diameter was given the metallurgy of the time when the pipe was first invented). Putting a tape measure behind the pipe is perfectly adequate, just subtract a fudge factor for pipe thickness (not much with copper) and snap to the nearest trade size. 5/8-ish diameter copper pipe is 1/2" trade. Regardless, I'd be far more interested in putting a thermometer on it. Commented Feb 7, 2018 at 20:36

4 Answers 4


My solution has nothing to do with plumbing, but since you mention the problem is in your basement and only in the winter, I'll throw this out there and it may help others...

I live in an apartment on the top floor of a renovated historic building. I like hot showers, and never was happy with the temperature of the water in the shower. It was passable in the summer, but taking a shower became miserable when cold winter weather set in.

For a long time I assumed the problem was that the water cooled down while traveling through pipes up to the top floor from a water heater that is presumably in the basement, and that lower ambient temperature in the winter made that worse. I doubted the landlord would change the water heater settings just for me, so I was all set to buy one of these and this and this to fix it for myself.

But then I realized that the cold air in the bathroom was at least partly responsible for my discomfort, since I was shivering as soon as I turned the shower off. So I made two simple changes. Before every shower, I closed the bathroom door, and blocked off the vent fan with a plastic bag, which stays stuck to the vent cover from the suction of the operating fan. (In this bathroom, the fan and light are controlled by the same switch. If the light is on, the fan is on.)

It made a huge difference. Since I don't turn up the heat that much in the apartment, showering with the door open and the fan on was pulling a basically unlimited supply of cold, dry air into the bathroom, and it was the evaporative effect on my skin making me feel extra chilled. But it's not just that the air temperature felt warmer. The shower water that had felt barely lukewarm before now subjectively felt hot.

I later added a space heater set to 65°F and that made the showers hot enough to turn my skin pink (the way I like showers). Someday I might swap that out for one of those electric towel-warmer-radiant-space-heaters.

So, to summarize, if you feel the water temperature in your shower is too low, you may be able to adjust your subjective experience of the water temperature by raising the air temperature and/or humidity in the bathroom.


Shower temperature is the minima of these things:

  • the temperature of the hot water supply, as it arrives at the shower valve
  • the temperature dialed into the cartridge (whose job is to not scald you). The cartridge does not set the shower temp, the handle does that. The cartridge sets the safety cutoff temp.

If either is below your desired temp, the other can't fix it.

If you have a tanked heater, it is important to turn it up to 60C (140F) which will kill deadly legionella bacteria. It will also scald you, so anti-scald valves (i.e. cartridges) are mandatory. This will have the side effect of raising useful temp at all your use points, giving your cartridge more "room to work with", and making hot water apparently last longer since you are using less of the hotter hot.

If you have a tankless heater, reduce flow. One big deal with a tankless is water inlet temperature. A tankless can only raise so many degrees for a certain flow. If your inlet water was 60F in the summer, and it was giving a 50F rise to 110F, that's great. Now that inlet water is 40F, it is giving a 50F rise to 90F, no fun. Increase rise by reducing flow. Tankless are often underspecced because the engineer used "by the book" sizing and "the book" presumes a modern California* house. Change your showerhead.

* it is the 1 year anniversary of the Oroville broken spillway/evacuation when the dam overtopped at 901'. You will not be putting your boat in the water today: water is at 723' and the ramps don't go down that far. This is why California specs low flow showerheads. If you're in the Great Lakes, not your problem but you still need to size your on-demand for your showerhead or vice versa.


The drawing shows the tick marks on the red part at the top. Is this part way out of adjustment?

The instructions say to remove the lock nut. Isn't the brass lock nut around the edge still in place? I would remove that and see if you can turn the red and black plastic parts about 170 deg counter clockwise to give what is shown in the diagram as the factory setting.

There must be more to the instructions that would help than what you have shown.


You have it upside down my friend. Put the red the other way with the plus and minus on top see if that helps.


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