hot water to shower not working as it should... All aspects of plumbing questions and answers, help, tips and information

[chris_on_tour2002]

trying to help the mother-in-law. she had a new bathroom fitted about 18 months ago and the hot water on the shower suddenly stopped working.

not sure of the make and model but it looks very much like a mira. i think that i've managed to establish that the cause of the problem is related to the temperature control knob.

i will try to describe the valve - its a thermostatic mixer, concentric valve and temperature control. so, when you open the valve, the control knob turns with it. seems to be the design, not a fault.

we are running the shower from a megaflow system with very high pressure from the main on both the hot and cold. (probably 20 litres per minute or more)

i took the temperature control knob off slightly so that it was clear of the 'stops', turned it fully to the left (ie highest temperature) and the water became luke warm. interestingly if i remove the shower head the water becomes roasting hot at the same setting. put the head back on and it becomes luke warm again. but at least there is warm water coming through now, which leads me to believe that it is the temp control knob positioning at fault here.

can anyone advise where i am going wrong? it seems to be either to do with the resistance of the shower head or i am not adjusting the temp setting properly. i've fiddled and tweaked with it for ages to little avail!

[simpleton]

I cant understand why the water gets hotter when you remove theshower head? That sounds like a limescale/dirt build up in the head. Other than that it sounds like the temp cartridge is on its way out. Good luck

[chris_on_tour2002]

thanks simpleton. it is curious as to why this is happening - the shower head has three settings on it that are selected by rotating the rose. jet, rain and a kind of mist setting. on the rain setting its ok - not as warm as it is when i remove the head from the hose but warm enough for a shower. on the mist setting the water becomes luke warm and on the jet setting it runs stone cold! its a mystery.

also, its a thermostatic shower. with no head on the hose the water is scalding hot. should this happen with a thermostatic valve even when the temp control is set to its maximum? does sound like the thermostat is on its way out.

[simpleton]

yeah it seems like a puzzler all right, you may have to use abit of guess work. I would start by popping a new thermo in, by the sounds of it you could end up becoming a regular visitor to the mother in laws