My combi boiler has the following filling loop fitted:
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I understand it by reading:
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end contains a stop valve and the other has a non return valve.
Our loop is installed with the smaller (lowest in the photo) end to the mains supply so I assume that this is the stop valve. Unfortunatly after quite a bit of use it seems to be leaking since our CH pressure is slowly rising.
We will be replacing the boiler in a few months so as a temporary measure can the other end operate as a stop valve, and if so how? tia Arthur
You might find an arrow on one of the valves indicating which directiom the water should flow in.
On my boiler, the larger valve is connected to the mains supply. However, we also had a leak when it was first connected and this was just down to a cheap/faulty valve, which was replaced without problem.
Incidentally, when you plumb in your new system, be sure to put the filling loop going in an upwards direction, ie like a n rather than like a u. It makes the addition of additives so much easier.
The water regs forbid the flexible tube from being left in place except during filling. So a leak in the stop valve should not be going into the heating system. (Actually, the reason is more to do with ensuring water from the heating system can't be forced back into the mains, even if the non-return valve and stop valve fail.)
If you have a combi boiler, another likely place for the leak is in the internal heat exchanger for the hot water supply. If, as you say above, you have been frequently topping up, then this will cause increased corrosion in the whole system, and might be the cause for the hot water heat exchanger to have failed. When the boiler is replaced, you must ensure such a system is very well flushed/cleaned before use with a new boiler, and that would be a good opportunity to have it pressure tested to find/fix all the leaks which are causing the need for frequent refilling.
Newer ones are supposed to have a serviceing (stop) valve at each end as well as a non-return (check) valve. You can get combined servicing + check valves, but I tend to install separate ones as I've come across a couple of installations where the check valve has failed and leaked back out of the CH system, and a separate servicing valve allows you to replace the check valve without draining down the system.
The stop valve will always have a screw slot or handle to operate it. The check valve will usually have a hexagonal head like the heat of a nut or bolt but this is not to be twiddled. There must always be a stop valve on the mains water side so that the filling loop can be disconnected (which you always do after filling, DON'T YOU? ;-) The filling point is also a good place to inject inhibitor, using e.g. a pump-up garden spray to force it in (via a suitable adaptor) (I really hate those Woosh Bosster filling keys for that reason ;-)
If the stop valve is a screw-slot type it's hard to be sure when it's turned right off unless you disconnect the filling loop. That'll also show you if the check valve is letting water back out of the system.
disconnect the filling loop (sorry to sound like a cracked record :-)
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