All single-handle faucets have a cartridge that controls the flow of hot and cold water. However, mineral buildup can clog this cartridge — which can keep hot water from flowing as it should. If you think you have a clogged faucet cartridge on your hands, you can try cleaning the cartridge.
Most likely it's either a clogged supply line, shutoff valve, or the actual hot water cartridge in the faucet.
It's a fault in the mixer tap. Try taking it apart and checking the rubber seals and the ceramic unit. Sometimes one of the rubber rings wears down and slips and blocks the flow. Might be as simple as replacing a rubber ring or as expensive as a new tap but most likely nothing to do with boiler rest of pipes etc.
Typically, when hot water is not working but cold water is, it could be a problem with the hot water heater or a blockage in the hot water line. A plumber should be able to help diagnose and fix the issue for you.Do you have a gas or electric hot water heater?
It is likely that the tub and the sink in the same bathroom are fed seperately from the hot water heater (that is the case in my house). There was probably a leak somewhere and the previous owner shut off the hot feed to the tub. Of course, it is a possibility that the tub has no hot feed.
Problem #1: Your anti-scald device might be set too high. If you're getting hot water everywhere but your shower, it could be that your anti-scald device is set at too high a limit. Anti-scald devices (also called a “hot limit stop” or “rotational limit stop”) are safety features that most faucets have.
Yours is probably inside the wall behind the shower handles if you need to access it. When you encounter thermostatic mixing valve problems, it's usually due to: Misaligned components.
Your hot water may not work for several reasons, from simple issues such as a tripped circuit breaker or a malfunctioning thermostat. Sometimes it's more complex problems such as a broken heating element in the water storage tank or a faulty water heater.
Open a Hot Water Valve
By opening faucets, water will have a path to flow as the pipe unfreezes. Steam will also need a place to go as heat is applied. As the pipe thaws, running water will accelerate the defrosting process. Therefore, it's beneficial to have faucets running until the pipe is completely thawed.
Somewhere on your electric water heater, you'll find a reset button. It's usually red and often located near the thermostat. It may also be hidden behind a removable metal panel on the unit—and then behind some insulation. Once you find the button, push and release it.
First, find the shut off valve for the hot water and see if it's closed. If so, opening the valve could remedy the situation. But if the water still remains warm for only short periods of time, you may have a blockage or obstruction in the pipes or a problem with your bathroom shower valve.
There might be a blockage or a leak in the pipes that supply hot water to your sink, resulting in a lack of hot water flow. Additionally, check if there are any closed or partially closed valves in the hot water supply line that could be restricting the flow of hot water to the sink.
If the problem is only with one faucet then it may be clogged. Is hot water coming from the other faucets in your home? If it isn't you might need the help of a plumber to fix. If there is only cold water coming from the tap, it is likely your water heater, especially if the cold side is working fine.
On a traditional single handle faucet, one with the handle on top (such as this Delta Foundations faucet) turning to the left is hot and turning to the right is cold.
Pipe-thawing options: There are several things you can do to thaw your home's pipes. Here's a list: Probably the most popular and safest pipe-thawing option is to use hot water. Wrap and secure heavy towel or burlap bag around pipe to concentrate and hold heat against it.
Likely places for frozen pipes include against exterior walls or where your water service enters your home through the foundation.
If you suspect that there are pipes in or above the garage, use space heaters to heat up that space as well. Make sure to keep heaters away from anything potentially flammable! Your pipes will eventually begin to thaw on their own once the temperatures rise above freezing.
Possible Issue: One of the most common culprits for this predicament is a malfunctioning differential valve. This valve is responsible for controlling the flow of hot and cold water in your plumbing system. When it's not functioning correctly, it can lead to an imbalanced water supply, leaving you with cold water only.
But you're hesitant to pick up the phone because you're not sure who to call: a plumber, electrician, or HVAC tech. So, what's the answer? Well, it depends on the issue. But for the most part, you should call a licensed plumber for all hot water heater problems.
If you can solder a copper pipe, you should be able to install a pressure-balancing mixing valve yourself. A decent-quality valve will cost about $125. The most difficult aspect of this project will be gaining access to the old valve inside the wall.
In newer homes, the water main shutoff valve is typically located inside or around the water heater closet. Very often, however, the valve can be in any number of places inside, or even outside your home.