Mixer shower woes. Can anyone help ?

[ekcopyephilips]

Hi All

Im totally perplexed by this problem and was wondering if anyone can help me solve it.
I have a thermostatic mixer shower with a power pump fed from a hot water cylinder, with the header tank in the loft about 1.5 meters above. All was working fine with this untill a few weeks ago. The pump started cutting out and the water only came through scaldingly hot. I thought it was the thermostatic cartridge in the mixer unit, so i contacted triton and got the correct replacement and fitted it. Still no joy. Cut a long story short a friend who is more au fait with plumbing told me that it had to be the pump, so today i fitted a brand new grundfos nile STR-1.5 C. Still no joy, with the pump cutting out if i try to turn the temp control to anything above freezing. I checked the header tank to make sure the outlet was not occluded (it wasnt) and disconnecting the inlet to the pump and opening the hot water valve i get a good healthy flow. The only things left to check are the cylinder flange (ive read i need a sussex flange, but dont know if mine is one of those or not) or could the bottom of the cylinder be thick with scale thus slowing down the incoming cold water and in turn slowing down the output flow of hot water. The system is fairly new as the house is only 10 years old. My next step is having to get a plumber in, but this thing in reality is so simple i should be able to sort it out myself.
So what do i check next ?

I really look forward to your advice

Cheeers

Mike

 

[seco services]

Did you change the flexis as well or use the original ones ?

 

[ekcopyephilips]

I used to original ones. I was wondering if i have an air lock on the hot water pump outpus side and there isnt enough pressure to clear it. Should i connect cold mains to this side and blast it out ? To my knowledge there are not any one way valves fitted anywhere

 

[seco services]

Depending where you disconnected the hot did you check the filter in the flexi to the pump ?

 

[ekcopyephilips]

Yup used new mesh filters, and flow to the pump from the hot water tank is good too.

 

[ekcopyephilips]

Hi All

Ive finally managed to fix this and now its all working correctly.

I applied a bit of logic and reasoned that the output from the pumpmust be occluded otherwise the pump should run. I disconnected everything and blew as hard as i could down the flexi tube on the outlet side. I couldnt get any air through, so there was definetly something blocking the hot water outlet side. Going back into the shower enclosure i noticed two large 17mm chrome bolts either side on the shower. I had wrongly assumed that these were there to hold the mixer assembly onto the wall - how wrong i was. On closer inspection i could see the faces of the nut were slightly marked, almost as if this had been undone before. So i undid the nut and hey presto, a small one way valve assembly came sliding out, and more importantly infront of this was a wire mesh - totally blocked with a brown fibre like substance. I cleaned it all off, reasembled everything and low and behold it all works as it ought to. I guess the morel here is to be logical and check the simple things first. Had i checked this weeks ago i would have repaired it in two minutes. Instead i have now shelled out on a new pump that wasnt actually needed. So anyone want to but a working second hand twin impella regenerative Grundfos pump ?

Cheers everyone

Mike