UPDATED: Very little cold water coming out of upstairs shower and taps

SuzieSue

Update:  In case anyone has the same problem.  southcoastrgi was correct, so thanks.  I tried putting my hand over the mixer tap as southcoastrgi suggested but it didn't work.  I called a plumber and he did the same thing but used the mixer in the bath and this time it worked.  


We have a conventional boiler system (cold water storage tank in loft (plus smaller tank next to it) and hot water storage tank in airing cupboard). 
The shower pressure has never been great, but for the last week we have noticed that there was very little cold water coming out of the thermostatic bar shower. 
We usually have the shower bar temperature set at around 38 degrees but since the cold water pressure/volume reduced last week, I have to set it at less than than 30 degrees.  
At first I thought that the thermostatic shower was faulty, but there is also very little cold water coming out of the taps in the sink as well, so I was wondering if there is a blockage or something affecting the flow or pressure of the cold water.
Thanks for any help.

neilmcl

Is it just upstairs or in the kitchen as well. Have you tried adjusting your stopcock?

SuzieSue

Thanks for your reply, kitchen is fine (it is from the mains) and the pressure is the same as it has always been and is very strong. 
I thought to start with that it could be the mains pressure (perhaps the water company was doing some work), but I then thought that the cold water pressure upstairs was due to the cold tank in the loft and so wouldn't be affected by the mains pressure? 
Is this not the case?  If not, then I will check if my neighbours have noticed anything.

TadleyBaggie

The upstairs taps and shower almost certainly are fed from the cold water tank, have you checked the level in it?

SuzieSue

Thanks, yes, I should have said. I went in the loft when it first happened and the cold water tank was full and the ballcock seemed to be working.

SuzieSue

There is also a smaller tank next to the large cold water tank and that also had water in it and the ballcock also seemed to be working.  Not sure what that tank is for?

southcoastrgi

The small tank is for your heating, do you have mixer taps in your basin ? If so put your hand tight over the spout & turn both taps on, you may have an airlock & hopefully this will force it out 

TadleyBaggie

My bathroom cold feed suffers from an airlock from time to time, shows up as a gradually reducing pressure which eventually stops the flow completely. It doesn't affect the shower however as that has a separate feed from the cold tank. To fix it I open up the cold tap, run a garden hose up the stairs and then force water back up the pipe into the tank.

neilmcl

SuzieSue said:

There is also a smaller tank next to the large cold water tank and that also had water in it and the ballcock also seemed to be working.  Not sure what that tank is for?

That should be the expansion tank for your boiler and central heating system.

Jeepers_Creepers

Hi SS.

If it's an air lock, then you'll likely need a hosed supply from your cold mains supply to shift it, as Tadley says above. You need to know what you are doing, and be happy to do it!*

First, tho', if you could go back up to your loft and shine a bright light into the large tank and see if there's any carp in it (you know I don't mean fish).

Is this a house or bungalow? If the former, where is the shower, and do you have a bathroom on the ground floor? If so, what's the cold flow from these taps like?

(*Another possible way to clear an air lock is to attach a garden hose to the cold tap in question (needs to be air-tight, but even 'duct' tape will do this), roll the hose outside and to the lowest point you can - even if just flat on the ground - and turn the tap on. The additional drop in outlet height will help draw the flow (once it gets going...) and could possibly suck the air bubble out with it.)