I hope someone can give me an idea whats wrong or point me in the right direction to sort it out. Out of the blue last night I suddenly have no cold water at the bathroom sink or shower (which is a fixed head spray thingy over the bath - the hot water is fine) and the toilet seems to fill up ok. I hoped it might right itself but it hasn't. Any ideas where I should start trying to remedy it?
The title of your post suggests that the cold water feeds to your bathroom sink and shower are from a cold water storage tank. What about the toilet? If this is mains fed rather than from the storage tank, it would explain why it is still filling up OK. To check whether the toilet is fed from the tank or the mains, turn off your mains water stop tap which is likely to be near the kitchen sink then flush the toilet. If it then doesn't fill up it will be mains fed.
Is the cold water to the bathroom sink and shower fed from the same storage tank that supplies the hot water system (cylinder)? If there is a separate tank for these, check that it has water in. If not there may be a blockage in the ball valve that fills it up. If it's the same tank as that which feeds the hot water cylinder or if it's separate and full there could be a blockage in the leg of cold water pipework between the tank and the bathroom cold water taps.
To try and clear a blockage in the pipepork, if you find that the toilet is mains fed, turn off your main stop tap again. Then disconnect the cold water feed from the toilet cistern and fix a length of hosepipe between this and the bathroom sink cold tap that is not working. Make sure the hose is securely fixed with jubilee clips and/or a hose tap connector, then turn on the tap on the sink. Finally turn the mains water back on slowly. The pressure in the mains water may then force whatever is blocking the pipe back up to the tank. Don't open the stop tap fully or if the blockage clears the flow of water forced back may be too fast for the tank overflow. Alternatively if it doesn't clear and the hosepipe blows off you'll have masses of water blasting onto your bathroom floor. If the toilet is not mains fed and/or you have a long enough hosepipe, you could connect it between the cold taps on your kitchen sink and bathroom sink. You wouldn't then need to turn off the stop tap to do it.
Sorry this is so long but I've tried to cover every angle I could think of. Good luck.
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