No hot water following tap repair.. Please Help

[Korgi]

Hi, can anyone help? Yesterday I tried fixing a leaky hot water tap in the bathroom of my purpose-built split-level 1960's maisonette (part of larger block). As far as I can tell, there's a single cold water mains valve in the kitchen that feeds the system consisting of a cold water storage tank upstairs (in my neighbours' loft to which I do not have direct access), all the taps and an immersion tank downstairs (which is electric, as I do not have a gas boiler).

So having done some reading on the web, I decided to turn the immersion tank off, shut down the water main, run all the taps and drain the system down in order to fix the tap. (for some reason the cold water upstairs and the hot water tap in the kitchen downstairs continued running at a sort of 1/5th of what I would call "normal' pressure, ie. not exactly "dripping" but "running" even though the mains water was shut down!) Mystified, I proceeded to service the hot water tap upstairs which luckily was dry.

Having fixed everything, I turned the mains water back on. After a while cold water started running upstairs as expected, but all hot water taps continued to be dry. I left them open, thinking maybe there's trapped air that needs to be released etc... Nothing happened. Normally water runs from these taps (regardless of whether the cylinder is heating water or not), but now I have no water coming out at all. Am I missing a trick here? Is the hot water cylinder supposed to be re-filled in some particular way? Any help greatly appreciated.

Bart.

[John Rumm]

You won't have actually drained the hot cylinder anyway[1], but it sounds like you may have ended up with an airlock (basically a large bubble of air in the pipework that prevents the usual gravity driven flow of hot water working correctly).

First thing to do is have a look at your hot water cylinder. The hot water pipe comes from the *top* of the cylinder, and at some point soon after it should split into two, with one side connected to a vent pipe that goes up to the loft space over the cold tank. If this is the case, they you have a normal vented system, and can carry out the following procedure without any risk:

The usual way to fix is this is to blow the air back out of the hot pipes so that they can refill with water. If you have conventional taps (rather than a mixer[2]) you can do this with a short section of hose. You open the hot tap, connect hose to it, connect the other end to the cold tap, and then turn that tap on for a few seconds. This should force mains cold water up the hot tap supply pipe, back toward the cylinder, where the air should be expelled up the vent pipe. Repeat this (perhaps increasing the time spent feeding in cold), each time seeing if water now flows from the hot tap normally.

If that procedure does not work, the other possibility is that some crud from the header tank has entered the supply pipe to the cylinder and blocked it. Probably time to call a plumber unless you are feeling brave!

[1] you can't usually drain a hot cylinder by attempting to run it dry, since the hot water comes out of the top of it - it relies on the cold being forced into the bottom of it due to the extra height of the cold tank in the loft to work. What you can do is shut off the mains cold feed to the tank in the loft, and run the hot until replenishing the cylinder has emptied the tank in the loft. [2] There are two types of mixer. Those that genuinely mix the water in the tap (only legal where both hot and cold are tank fed), and those with concentric spouts that mix the water as it leaves the tap. The first sort are the easiest to deal with since you can achive the joining of hot and cold simply by sticking you hand over the end. With the concentric spount type you may need to place a strong plastic bag over the end of the spout and grip it tightly in place to achieve the coupling.

[Korgi]

Cheers John, genius advice. It did the trick. Looking forward to a hot bath later:)

Many thanks. Bart.