Help regarding my hot water cylinder

31 Oct 2010
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United Kingdom
I just returned from holiday and I may just becoming paranoid but my system appears to constantly have a rushing water sound when the hot water comes on. I swear it never made it that noise beforehand.

I have a potterton boilder in the kitchen, the two water tanks in the loft, and a hot water cylinder in the airing cupboard. It just sounds like there water constantly running around the system, although the hot water does appear to be fine when I run it, hence me not sure whether I'm imagining something that has always been there.

Another thing I noticed is that there fullway valve at the front of the cylinder which is in the close position and is cold, however when I trace the pipes back either way, about 10 inches away the pipe is hot. Should this valve been open or closed (see photographs).

Any help is appreciated.

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The valve in front of your cylinder is a bypass valve, its looks like your system is a 'y plan' so providing you have atleast 1 rad with no trv this should remain closed.

You may want to jump in the loft to check your f&e tank (the small one) to make sure its full, you may have a stuck ball valve resulting in air in the system giving you the 'rushing water sound'
thanks for the advice, i've made sure the valve is closed and checked the small tank, it wasn't stuck but the water is not that clean - appears to be due to build up of something along the side of the tank. i'm a total novice re this type of setup as all my previous homes have had combi boilers - how do these 2 tanks work together, and what do the contribute to ? By that I mean are they simply cold water sources which use gravity to keep the hot water tank and radiators, and if the water in that small tank (the large one is very clean) is that dirty (a brown colour) how is it made clean when it comes out the taps ?
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Large tank is cold storage. This feeds the cylinder, where it is heated and drawn off to hot taps. Smaller tank is Feed and Expansion for the central heating system. This is completely seperate from the hot water supply, the two lots of water do not mix unless there is a fault with the cylinder. Both work on gravity supplies as you have said.

Ideally the central heating system water should contain inhibitor. This prevents a chemical reaction between the different metal components of the system which leads to dirty water and sludge in the system. If the water is brown its a good indication that there is no inhibitor present. Not an immediate concern, but can lead to problems over time.

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