CH Pump

rootoo · 26 Jan 2006

Hi, We've presently got a Myson Compact CP53 pump and it's started to sound a bit rough and get very hot, the rest of the central heating system's fine and only 7 years old. Before it dies on us I'll like to replace it. Could you please let me know if the Grundfos Selectric Bare 15-50 130mm would be a direct replacement. We have isolation values either side of the pump so we have to go for a 130mm pump but I'm not sure if the Grundfos has the same connections, the Myson looks like it has 55mm connections.

Thanks

ollski · 26 Jan 2006

pumps are standard, but depending on which valves you have they will probably (almost certainly) leak if you go anywhere near them with a scredriver.

ACOperson · 26 Jan 2006

If the valves have spindles on them which are turnable with a spanner to isolate you might be alright.

If they have small isolation valves which you put a screwdriver into and turn 1/4 of the way to isolate then 99% of the time they will need to be replaced along with the pump. The pipes will also need chopped around 1" to accomodate new 'gate' type valves.

rootoo · 26 Jan 2006

Thanks for the reply, looks like we'll be draining the system, is it worth replacing the isolation valves while we're at it.

corgiman · 26 Jan 2006

I would say yes to that just so as you know that they will work the next time you have to change the pump.

ACOperson · 26 Jan 2006

Yeah replace them. After installation, fully open the isolation valves, then give them a quarter turn the opposite direction (closed), they will be easier to turn off in the future.

rootoo · 26 Jan 2006

Thanks for your reply OCAperson, I've just had a look and we have valves that require a spanner, there is a square tip to the spindle and nowhere unscrew with a screwdriver.

Do you think we can keep these or should we replace, they also act as a reducer going from the pump down to 22mm. I think we've decided to drain the system upstairs. Would it be a good idea to clean the system at the same time, it's not been touched (other than bleeding the rads in 7 years)?

Cheers

ollski · 26 Jan 2006

rootoo said:
Thanks for your reply OCAperson, I've just had a look and we have valves that require a spanner, there is a square tip to the spindle and nowhere unscrew with a screwdriver.

Do you think we can keep these or should we replace, they also act as a reducer going from the pump down to 22mm. I think we've decided to drain the system upstairs. Would it be a good idea to clean the system at the same time, it's not been touched (other than bleeding the rads in 7 years)?

Cheers

You may be lucky with these and they may just require the gland nut repacking if anything at all, however be prepared for the fact they may well not hold shut and if you are relying on them to remove the pump then loosen the pump head to drain it, if you get more than a pump full then drain it down. If you replace the valves then use heavy duty ones but bear in mind they will almost certainly be longer.

ACOperson · 26 Jan 2006

You might be lucky if they are in OK condition.

However as previous post says, they may let by and if this happens you will get wet! Drain a bit of water from system, isolate the pump valves and pray to the god of plumbing...

ChrisR · 27 Jan 2006

Myson pumps were made by "Circulating Pumps Ltd". They go under other names too.
If you get the same make you'll be able to just change the body.
EG these:
http://www.bes.ltd.uk item 10805

Softus · 27 Jan 2006

So, to recap:

1. The valves might hold up.
2. The valves might not hold up.
3. If they hold up then you are lucky.
4. If they don't hold up then you are unlucky.
5. Even if they hold up, then it would be prudent to renew them.
6. Even if you renew them, there is not one single iota of a guarantee of any sort that they will hold up when you come to change the pump again.

Should I now create another eight posts to make sure that I've got it right?

Soggy_weetabix · 27 Jan 2006

and if they hold or not....lots of silicon grease around the pump thread, and absolutely no jointing compound or tape around the washers / threads.

Oh, and rubber not fibre washers if you please.

Your pump will literally fall out when you have to change it again if yo do that.

Gate Valves hold (or literally hold) in my experience 75% of the time. By saying literally though, you have to get the new one in quick!

On a slugded system, if you install new valves they will in effect not operate in 6 months anyway, but always Gate type and never ball.

David

ollski · 27 Jan 2006

Soggy_weetabix said:
Oh, and rubber not fibre washers if you please.

Sorry mate but I would say completely the opposite.

Softus · 27 Jan 2006

My vote is for rubber - fibre ones don't go the distance.

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CH Pump

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