Combi Boiler / Shower Issue

[ashfp]

Hi All,
I fitted my bathroom about a year and a half ago now. I changed the shower from an electric powered one to being fed from the boiler. It has been fine (good water flow/pressure and always good temps), but for the last few months I have had the issue of reduced pressure, and intermittent hot water. Usually it will be hot (not great pressure, but ok) for about 5 minutes, then it will go cold, and sometimes it will come back on hot after another couple of minutes (but sometimes can take longer and once just had to get a cold shower).

My usual plumber is too busy to come look but he suggested it was the mixer tap not the boiler?

The boiler is a "baxi platinum combi 28 he" and the mixer tap is "ULTRA THERMOSTATIC BATH SHOWER MIXER VBS004".

Any thoughts?

Much appreciated,
Ashleigh

 

[bernardgreen]

Almost all combi boilers have a maximum and a minimum flow rate for hot water supply. Take more water than the maximum and the water will not be as hot as normal, take less than the minimum and the boiler will shut down to avoid producing scalding hot water.

They don't really suit showers.

If you are in a warm shower and someone turns on a hot tap fed from the same combi then the hot supply to the shower will be reduced in either flow or temperature and the shower goes colder.

Several people I know who were convinced by plumbers that a combi was the way forward have had to fit an electrically heated shower.

 

[ashfp]

Almost all combi boilers have a maximum and a minimum flow rate for hot water supply. Take more water than the maximum and the water will not be as hot as normal, take less than the minimum and the boiler will shut down to avoid producing scalding hot water.

They don't really suit showers.

If you are in a warm shower and someone turns on a hot tap fed from the same combi then the hot supply to the shower will be reduced in either flow or temperature and the shower goes colder.

Several people I know who were convinced by plumbers that a combi was the way forward have had to fit an electrically heated shower.

I can see where you're coming from, but it's not been an issue for over a year (even when turning on the kitchen tap, the shower wouldn't really greatly effected).

 

[Terry7556]

Ashfp
How old is the boiler,has it been serviced, if so when was the last time
Does the problem occur anywhere else in the house, at another hot tap ( I mean running hot/cold/hot)
If you remove the shower head from the hose and run the shower while holding the hose in your hand ,does the problem still occur
Come back with those answers which may help to decide if it's a shower or boiler problem

 

[gazplumber]

Ashfp
How old is the boiler,has it been serviced, if so when was the last time
Does the problem occur anywhere else in the house, at another hot tap ( I mean running hot/cold/hot)
If you remove the shower head from the hose and run the shower while holding the hose in your hand ,does the problem still occur
Come back with those answers which may help to decide if it's a shower or boiler problem

Ashfp
I had similar shower problem recently. Limescale had partially blocked shower head and flexible hose, reducing water flow and causing boiler to shut down in HW mode.

Clean or preferably replace shower head with one with more jet holes in the head. You could also replace shower hose with one with a larger internal bore size. Both these actions will result in greater water flow keeping boiler firing in HW mode.

gazplumber