pump valves

4 Feb 2022
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United Kingdom
Please can anyone advise.
My house was built in 1983
The central heating pump fitted during construction was a SMC Commodore 2. The model number was 2-130-60 type Cast Iron pump case length 130mm.
At some time later due to a problem British Gas changed the motor head to a Multi-Head 11.
I am considering changing the pump to a Grundfos UPS3 15-50-65.
My issue is the pump valves, there is not much room to undo the pump connections. The are currently 22mm/
bsp11/2 inch gate valve type. ( The gate valves turn ok so no problem there) I think I may have a problem undoing the bsp nuts. ( If need be I might cut the bsp nuts and replace them if I can bet them)
Worst case I may have to replace the pump valves. Having researched new pump valves they seem to be shorter than my originals. The attached photo shows an approximate length of 70 mm from the top of each nut to the other, is this the normal length.?
Your advice will be greatly appreciated
Regards Mike

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I wouldn't rely on the Pump Valves shutting off, for peace of mind, I'd drain the system to below the pump and allow for replacement valves with the new pump. Any shortfall can be made up with a piece of 22mm tube and a coupling.

Why are you wanting to change the pump?
Bought these last year. You just need to look a bit harder.


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Thanks for your reply
Pump is making a gushing noise. I checked again this morning the pump is working but and hearting hot water cylinder , however the motor head was extremely hot.
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