Is this an isolator valve for central heating pump?

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Hello everyone,

Can someone please confirm if this (marked in red in both pictures) is the isolator valve? If so, will shutting this off will prevent water to flow to the 3 port valve connected below the pump (picture2)?

We need to replace the 3 port valve body and need to know if we can do this safely by shutting off this valve.

Thanks.

Picture1:
Picture1.jpg


Picture2:
Picture2.jpg
 
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1. Yes, it is a valve. Called a pump valve rather than an isolation valve to be picky. That type, with a screwdriver slot, are generally pretty useless.
2. No, it won't stop the flow. You will still get water flowing back from the pipework attached to the outlets of the motorised valve.
3. Are you sure you need to replace the valve body? Remove the actuator head (white plastic bit) and see if the valve spindle turns relatively easily. If it does, and there are no signs of leakage around the spindle, why not just replace the head. No need to get wet!
4. If you buy a complete new valve (looks like a Drayton) you could just use the actuator, and only change the valve body if it proves necessary.
5. To change the body you will need to drain down so that the system water is lower than the valve. If you really know what you are doing you might be able to avoid the drain down.
6. If you do decide to change the whole valve before buying, I'd recommend replacing the Drayton with a Honeywell valve. However, you would have to remove the compression nuts and olives on the inlet pipe and outlet pipes, as the Honeywell has different threads on the compression fittings.
 
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It's a brave man who's prepared to touch those pump valves. Fiver says at least one of them will spray water at you if you try to operate them
 
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oldbuffer, thanks for the detailed information. Very useful and after reading your reply, realized that the water from the cylinder will definitely flow unless it's empty. The other outlet is going downwards to perhaps less chance of water flowing with the system shutdown (I'm guessing?).

On point 3, I'm sure it's the problem with valve body. Basically, the actuator often gets stuck and doesn't move fully from 'H' to 'M' (and vice versa). But when unplugged, it works perfectly. And the spindle is not smooth at all, I have to use a plyer to move in the right direction. This actuator is around 1 year old and was replaced by insurance. The engineer also noticed and mentioned that the valve is clogged and will need to be replaced eventually. It definitely needs to be changed now as the valve is getting stuck more often.
 
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It all depends how much pipework/rads etc that is heading out of the A and B legs of the valve is above that valve, that will determine how much water will need to be drained. Is your system sealed or is it gravity fed?

Only the water in the supply pipework and coil of the cylinder will drain from port B, just in case you think all the HW water in the cylinder would drain out.
 
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realized that the water from the cylinder will definitely flow unless it's empty.
The water from the cylinder wont go anywhere,if you are doing a partial drain down to change the valve change the two ballofix pump valves for gate valves at the same time
 
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