No hot water at bathroom sink

Another problem:
BTW, after I'd pretty much agreed to rent this room, she told me it needed a lot of repair. But none of the problems I've found actually affect me much. This one affects me a little.
She has hot water everywhere but the bathroom sink. The hot water comes from the laundry room and it's available at the washing machine and the kitchen sink and another line goes off to the bathroom, where it's available at the shower and the bathtub but the sink is the last outpost on that line, and there is none or next to none. This started after they did digging outside, on the cold water pipe, of couse, but if that is the cause, somehow it's only affected her hot water.
The pipes are behind a beautiful tile wall. It's at least 6 feet from the bathtub to the sink**. The valve under the sink turns easily, quite a bit from off to on and I'm sure it's all the way on. I guess I'll turn it on and off a few more times, but .... Is there any point to taking the valve apart on the hope that the blockage can be pried to pieces with an awl or something?
The faucet itself is one-piece, one handle, and when all the way to hot, almost nothing comes out, and it's not hot. Maybe the blockage is between the valve under the sink and the faucet, but I have no idea how to take this strange faucet apart. ?? She's short of money or she wouldn't be renting me the room in the first place, but the rent I paid her will go fast if she spends it on a plumber, and heck it's broken. What an opportunity for me.
**Here I was assuming that the problem was only at the sink. Now I see that the diverter at the bathtub won't allow the shower in the tub to be turned off completely, and the hot water pressure at the tub is much lower than the cold water pressure. I've taken a shower, but even in the US I don't understand the one-handle shower valves so I'm not sure if the hot water pressure is low there too.
I can get a little more information but this is most of the facts. What would you do next? What do plumbers do in this situation short of ripping out the tile and the hot-cold water controls?
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On 04/14/2017 02:20 AM, Micky wrote:

The blockage is not likely to be in the middle of the pipe, so it's probable that it occurs at a bend.
Turn the water off in the house and remove the shut off valve under the sink. If there is no shut off valve just remove the pipe itself and see if the passage is blocked
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Turn off the water to the house, then disconnect the sinks hot water hose from the shut-off valve under the sink. Look inside the shutoff valve as you open and close it (use a mirror and flashlight if you need to). You should be able to see the valve opening and closing inside. If not, the shut off valve is probably broke and will need to be replaced.
If the valve appears to be working, connect a hose to the valve and place it in a container. You can use the hose that runs to the sink if you can access it. Then turn the water on and open the valve. If water comes out you know the clog is in the sink faucet. If water does not come out there is a blockage somewhere in the water line before the shutoff valve.

If you determine the faucet is broken, it should be fairly simple and inexpensive to install new washers, seals, or cartridges.

Do you know what kind of plumbing you have? If it's old galvanized pipe, it may have corrosion build up inside restricting water flow. If that's the case, the only option is to cut out the pipe and replace it.

Most single handle shower valves have pressure balancing valves in them. This allows the valve to balance the hot and cold water so you don't get scalded if someone flushes the toilet or something.
Pressure balancing valves can stick, which would typically give you only hot or cold water when you turn on the shower.
Anthony Watson www.watsondiy.com www.mountainsoftware.com
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On Friday, April 14, 2017 at 11:17:21 AM UTC-4, HerHusband wrote:

And the pressures on each supply have to be fairly close. These valves will shut off one side if the pressure is more than 5 psi greater than the other. That number was quoted to us from the manufacturer, so I'm not sure it applies to all brands.
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On Fri, 14 Apr 2017 15:14:12 -0000 (UTC), HerHusband

In North America for the last 10 years or so pressure balancing faucetes have become popular, but the lower priced stuff still doesn't have PB valves (and none in my house do). I rather doubt the house in question has high end fixtures.
Also, since both the tub and sink have low pressure, and given the age of the place. I'd put better than even money it's got some old galvanized pipe - and the hot lines plug up before the cold generallt speaking.
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I did not catch how old he said the house was.
If it was built in the last 15 years or so, most plumbing codes require some form of anti-scald device on a shower. The pressure balancing valve is the type I am familiar with, but there may be other designs too.
If the house is older than that, it probably does not have a pressure balancing valve unless the shower valve was replaced in recent years.

I agree that's the most likely cause, but valves do stick or break so it's work checking. That's certainly a lot cheaper and easier than replacing plumbing pipes.
Anthony Watson www.watsondiy.com www.mountainsoftware.com
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On Friday, April 14, 2017 at 3:20:40 AM UTC-4, Micky wrote:

Easy test. Switch the hot and cold hookup to the sink. It will eliminate 'expensive' test.
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