NO hot water upstairs on valiant combi boiler

[haquea]

I am having problems with the hot water upstairs on a valiant Combi boiler, its about 10 odd years old, the last work on it was a replacement diaphragm i believe a year ago . The hot water downstairs is fine but upstairs shower has no hot water and the bathroom sink taps run infrequently luke warm to cold .
Pressure on boiler says 1.5 bar . there is a header tank in the loft ( assume this is a F&E tank for the CH? ) . When the diaphragm was replaced the plumber also said there was blockage in the hot water pipe near the boiler which he cleared out, which improved water pressure upstairs ( although hot water coming out of shower head was never 100% , it sometimes blew hot and cold with interment low pressure) . The pressure out the hot water taps seems ok at the moment .

Is this as simple a a case as descaling ?

 

[stevetheplumber]

if you have a combi there shouldnt be any tanks are you sure they are connected?
probably either three way in boiler or secondary heat exchanger scaled/blocked

 

[diamondgas]

:welcome: to the forum haquea 🙂

the usual suspect for the symptoms you describe is the diaphragm. Seeing as you've had one replaced though you really need to know what is happening with the boiler when a tap is ran upstairs; is the boiler staying on, diverter valve not passing, boiler producing enough heat etc.etc. Knowledge of whether you're in a hard water area or not is also a benefit when you consider scale! Would also need to know whether the taps in question are thermostatic mixers or not?

Not such a simple answer eh?

Best bet is to get someone out to give you advice IMO ... You can post your general wearabouts on the "I need a plumber/gas engineer" forum and see if you get any response from someone local to you 🙂

 

[haquea]

thanks, the main offender is the shower that is on a thermostatic mixer, sink taps are not, and they tend to work intermittently but don't always get really hot . I am in east london which i believe is a hard water area

 

[haquea]

on another forum, a plumber said he would come and descale for me for 120GBP . he seems reputable but seemed like a bit of a quick conclusion ?

 

[diamondgas]

on another forum, a plumber said he would come and descale for me for 120GBP . he seems reputable but seemed like a bit of a quick conclusion ?

I'd agree without assessing the issue it may be that the shower temp cartridge is no longer working. Is your vaillant a turbomax by any chance? 3 green dials for control?

 

[haquea]

no, i couldn't find the model no on it, but it has 2 green dials . if it was a shower temp cartridge ( assume this is in the shower unit ?) then what be affecting the taps blowing hot and cold as well ? downstairs everything runs fine, not sure i mentioned that before

 

[diamondgas]

no, i couldn't find the model no on it, but it has 2 green dials . if it was a shower temp cartridge ( assume this is in the shower unit ?) then what be affecting the taps blowing hot and cold as well ? downstairs everything runs fine, not sure i mentioned that before

The basin and bath blowin hot/cold and none thermostatic would have me looking once more at the diaphragm/diverter. Especially if you have no issues with water temp and consistency downstairs!

The Vaillant Turbomax has a hinged door that swings to the side .... Black plastic behind it with the green stat controls mounted vertically on the left

 

[haquea]

im not at home but that does look very much look like my boiler from memory, and the door does open to the side . what does it mean if its a turbomax?

 

[diamondgas]

im not at home but that does look very much look like my boiler from memory, and the door does open to the side . what does it mean if its a turbomax?

Well without the ability to have your boiler infront of me I'd be more inclined to look at the diverter diaphragm once more or the valve its self! If your water is getting hot and staying constantly so at lower level but not upstairs the only difference is the height to tap which must decrease the flow through the boiler. This fault usually shows on relatively poor cold water mains flow also, by the way!!

 

[haquea]

been told the DHW heat exchanger needs descaling from a chap who came round for a 5 min diagnostic . 140gbp, that sound like it will do the job ? he said i could also change the heat exchange but would cost about 280 gbp

 

[haquea]

is there any reason why you would want to change a plate exchanger instead of just having it dipped in acid and cleaned ?

 

[diamondgas]

One in, one out and no hanging about :lol: