HELP ME - new shower not working

missy_brambles

I have had a new bathroom installed in past 3 weeks - its beautiful - but the shower doesnt work. Mostly I have no hot water to the shower as the shower wont fire up my combi boiler (17 year old vaillant). Other times the shower gets hot and then goes cold whilst I am showering and I have to finish my ablutions in the bath.The plumber has fitted a thermostatic bar type shower valve - no make shown on shower. The plumber thinks the problem is with the boiler - although I had no probs with my old shower. I have had my service engineer look at the boiler, he says boiler is okay. Plumber is now failing to ring me back with answers. Any ideas - by the way, plumber has been paid in full already!!!! I'd be very grateful for some guidance.

Paul_the_Painter

Two possible problems I can think of.

As you have a combi boiler you may not be getting enough flow through the boiler to trigger it to light. To check this turn on a sink hot tap, and leave it on while you take a shower, if everything is now OK you either have a low water flow throught the shower, or the boiler is not firing up as soon as it should (17 years is good going for a combi boiler)

Second possible problem is debris in the thermostatic valve, from fitting the shower.

Check the tap thing first, debris would be a problem for a plumber

bestyman

Hi,
First thing to find out is if the shower is compatable with a combi as some are designed to be tank fed. If not sure how to find out post model and I will tell you .
Assuming the shower is suitable it could well be a fault with the combi, well not exactly a fault more of a worn combi. does the combi fire with a normal hot tap half open? if not susbect a dodgi combi.

Combis work like this, when water flows through it it triggers a flow switch that lights the main burner. Now if not enough water is flowing through it the main burner won`t light and if you have an old combi the flow switch might not be as sensitive as it once was. Try the following:
Try operate the shower without the head and if possible hose connected, if it works then try a different head with more holes in it and a larger bore shower hose.
I assume your water pressure is not the best, make sure all stoptaps are fully open. If your pressure is low in all taps in the house mention this to the water board who may increase the pressure ( eventually). It helps if neighbours complain too.
As posted earlier they may be debris in the inlet filters, have a plumber check this.
Lastly the plumber may have put it in wrong. Problems could be hot and cold connected at the wrong side, kinked pipe or left bending spring in. Isolation valves not fully open ( maybee have them changed for ones with full bore as standard ones restrict flow.)
Well thats about all the possibilites I can think off. I`d try it without the hose first.
Paul

missy_brambles

Many thanks for your advise. I have just had a sleepless night worrying. It is true that the pressure isnt what it should be. I am told that the water board are obliged to supply btwn 1 and 6 barr (is that the right technical term?) and that my supply is 2 barr so a bit on the low side. I am just about to test the first theory. wish me luck..

missy_brambles

Ok here goes. I have managed to have a hot shower - yipee... I achieved this by running the hot water tap till the boiler fired, I then turned on the shower. However the water flow from the shower was too weak to shower under, so I then turned off the hot tap, the pressure to the shower increased and stayed hot whilst I showered. So I guess that pretty much says its a water pressure thing and it isnt high enough to fire the boiler from the shower (didnt it?)
couple of questions though.
why does the boiler fire from the taps and not the shower? - surely the low pressure is to all of the water outlets.
Is there possibly a shower valve that is more compatable with low water pressure?
Is there anything that can be attatched to the boiler to increase the water flow - ie, a pump of some sorts?
Why did my old shower work perfectly for 9 years?

Sorry if any of these questions seem to be stupid but I'm sure you've guessed it 'I know nothing'
Many thanks in anticipation

bestyman

Hi,
The boiler works ok from hot taps because they let water out unrestricted while the shower head has lots of small holes that restricts flow. This is why trying a different shower head may work. Try one of the multi mode ones on the different settings .
If Argos sell em you can take it back within 14 days if unsuitable.
Paul

squeaky

When you turn on a hot tap - the tap is wide open so the water pressure drops from whatever your normal is to almost nothing.

Your shower on the other hand has a spray nozzle that deliberately restricts the water flow to keep the pressure up (and that's how you get a nice jet) so the pressure in the system doesn't drop so much.

Pauls good suggestion of opening the h/w tap first was what triggered the heating because of the big change in pressure - then you took advantage of it by then using your shower which can't do it on its own.

There's a way to adjust this trigger pressure on my boiler and it's in my instruction book

maybe Paul can tell you, or if it's a plumber job.

Paul_the_Painter

I have no idea how to adjust the trigger pressure! I would take the advice of a plumber, but tell him the problem with the shower, and how you got it to work, if the trigger pressure cannot be adjusted you may be better off with a non thermostatic shower, as what may be happening is after a bit the whole shower heats up, as well as the pipework so the shower is seeing hotter water from the hot supply. This will then prompt it to reduce the flow of hot and increase the flow of cold, that could well take the flow below what is needed to keep the boiler running.

This could also be cured by making sure you have enough pressure at the mains, the water company has to provide you with a minimum pressure, if you are not getting this they can rectify it. You may also be able to have a booster pump fitted before the combi boiler to increas the pressure, but I am not sure if that is possible.

squeaky

Oh well There's a plumber about the place somewhere too - plumb1 I think?

Pink.

Hi missy brambles,

The thread you started in Anything Else has been moved over here, so I have merged the two threads and deleted any duplicate posts. I hope that you get the shower sorted out soon

Pink

bestyman

Hi,
Me again. (I am a plumber)
Most combis don`t have an adjustment for the sensitivity but some do have a flow /temp for the hot water . Worth a try but not holding my breath.
Have you tried it without the head yet or with a different head?

If all else fails why not ring the shower manufactorer to rectify (if possible) the faults . That way you have written evidence of the cause of the fault and can claim from the plumber if it was his fault.

Paul ( sorry this is confusing 2 pauls lol )
ps
Pumping a cold supply to a combi ( or hot out, same thing) is not really an option as , how do I explain, you cannot pump what isn`t there , pumps are usually used for showers that are tank fed .
The old shower worked because , for one reason or another, water flowed through it faster.