I am having a problem with the hot water in my upstairs bathroom. I have tankless hot water.I have the burner cleaned every year There is hot water in the shower for only a minute then it is lukewarm. The same is true in the sink. Hot water downstairs is fine. I have had a plumber here twice and still no hot water. He has changed a reverse value and a temperature value. He now wants to try changing value in shower-I am just not sure why-How will this help hot water in the sink. Seems to me it has to be something else. I would appreciate any help. I live alone and have no idea what to try next. Thank You

Hi if you have a gas combi boiler this guide below may help .

If the temperature in the home drops below the pre-set level, the room thermostat sends a signal to the boiler to fire up so that heat can be directed into the central heating system. The opposite happens when the thermostat detects that the required room temperature has been reached.

When there is a request for hot water - triggered by someone turning on a hot tap - water is heated inside the combi boiler which then flows through to the relevant tap.

Control valves inside combi boilers operate in different directions, either letting the water pass through to the hot water circuit or diverting it into the central heating system, as required i.e, hot water either flows through the central heating system or to a hot water tap/shower when required, but never both at the same time.

Important factors affecting operation

Combi boilers require sufficient mains water pressure in order to deliver a good water flow rate; low mains water pressure means hot water will merely trickle. If your mains water pressure is low or you have more than a couple of bathrooms, a conventional system boiler might be a better option for you. Try our Product selector to find out.

It is also important to ensure that the heat output of the boiler is correct for your needs. Combi boilers have two heat outputs: one for Domestic Hot Water and the other for Central Heating. More effort and hence more heat is required to produce hot water than to heat a home through the radiators, so it is usually the hot water output that determines your choice of combi boiler. A gas safe registered installer will be able to help you determine what boiler you require to meet your needs;

Hi Jem

You said, "He now wants to try changing valve in shower-I am just not sure why"...

He may want to change the balancing spool/cartridge in the shower valve because he suspects that the spool/cartridge is defective and allowing cold water to mix into the hot water even when the valve is shut down... basically creating a cross-connection and causing the issues you mention.

Is this reasonable? Well, considering that you say the other faucet(s) in the home don't have the issue, just the ones in that particular bathroom, then yes, it is reasonable!

If the washing machine is close by you want to shut off the hot or cold water supply to the machine via shutoffs and be sure that the washing machine solonoid valve isn't the culprit creating the issue here. It is certainly a quick check to find out (and costs nothing)!

Does all this make sense?

Mark