My shower is running cold water only, the rest of house has hot water

Your whole house is likely plumbed wrong so that it is impossible to have equal pressures of both hot and cold at your shower. If you had your home plumbed with aquapex using a radiator for the hot water and a radiator for the cold water and have the radiators fed with a 1 inch line you can have close to perfect pressures.

There should be a hot water limiter behind the knob on the shower - shingle handle, undo the handle and move the adjustment to allow more hot water. Not familiar with mira discovery mixer

If I understand correctly, you have single handled shower faucet.
Normally there is a wait for hot water to arrive at faucet.
But now hot water is already at shower faucet.

Single handled faucets have a mixing area inside valve where hot and cold come together before going into sink.
This mixing valve can have crossover where the hot and cold can pass through to each other even when faucet handle is off. When single handle faucets get old, this can happen.
How it happens:
For example another faucet is turned on inside house, and pressure differential between hot and cold causes hot water at shower handle to pass through mixing area and into cold water line.
So if another faucet has been run, then that lets hot flow to faulty single handled shower faucet.
To confirm this is the problem: turn on other faucet and put ear against shower faucet to listen for moving water.
This condition may also signal there is a water leak.
The problem is not harmful, but will draw cold water into water heater each time, and is energy wasteful.
Replace faucet or have plumber repair problem.

Screw off shower head-obstruction in water saver disc or screen,piece of rubber or rust

Hi im Rossouw

The rest of ur house water in the showers fine?
If not they must install a prv (Presure reducing velve) on the cold going to the house and geyser befor it t,s of to the house and even if the rest of the house water is fine u must ask ur plumber who intalled it if he took the cold water going to the new shower strait of the mains if so he must corect it by t-ing in at the right cold water supply or put a velve on the cold water to ruduse the cold presure . then u will have more hot presure and that means lovely hot shower

plz vote and rate my advice thanx

The plumbers screwed up when they installed your showers. There are two connections on each shower. one for hot and one for cold. they connected the two hot water lines together with a T fitting and then ran a line to the main hot water line and tied it in. Then they connected the two cold water fittings with a T and ran that line to the main hot water line and tied it in there instead of into a cold water line like they were suppose to. This is the only possible logical solution to this problem. They tied your cold water connections to both showers into a hot water line instead of a cold water line.

Hello, first if any water supply hot or cold is turned off, you will experience trickling as you mention. You must have both cold and hot in order to adjust the temperature on your valve. if you had a plumber intall this unit you should ask him to adjust it. Otherwise here is how:
Rotate the handle counterclockwise to stop and let water run till cold water is purged, check
temperature. Rotate handle to off, remove handle parts (see Disassembly in your manual) and temperature limit stop, rotate clockwise to decrease and counterclockwise to increase maximum hot water temperature, reinstall temperature limit stop and handle (TIP: Do not screw handle in until desired maximum temperature is achieved) Repeat steps until desired maximum
temperature is achieved

It sounds like you have a faulty thermostat or broken heater element.

The problem is solved, it was a single handle shower valve in the open hot position when my wife washed her hair, she turned the water off at the shower head. This forced hot water into the cold pipes when a faucet down the line was opened. Thnks for the help.