Myson Pump Seized (Potterton Suprima)

24 Oct 2016
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United Kingdom
Hi All

I just moved into a house with a 20 year old conventional central heating system (Potterton Suprima 40L, Hot water cylinder , Cold water tank in the loft, Myson CP53 pump)

Last weekend the Myson pump seized causing the boiler to go into lockout everytime it was switched on. After looking at the Internet, I removed the black cap on the pump and turned the screw to loosen it. It worked again after that.

I did notice that there was black water coming out of the pump , some noise when the pump is running, and it is running a little hot.

What would be the best course of action ..(If it were you, what would you do)

- Replace the pump with a new , more reliable one (groundfos?)
- Replace the pump and powerflush the system to remove sludge
- Forget about the Potterton and replace the whole boiler and system with a Combi
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You did not read the internet very well. The black knob can be used to turn the nut. In fact that is what it is for!

Because pumps are magnetic when operating they tend to attract black iron oxides.

Ideally try to drain/clean the pump to get rid of the oxide.

The rest of the system might be dirty and you need to check that and if so to clean it.

Do not replace the pump if the system is dirty. Otherwise a new pump will be spoilt on a dirty system.

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Wax capsule in a Suprima, and apparently it will work ok with a duff pump. Another load of useless misinformation. Change the pump Alex. While doing that drain off some water and check for possible sludge. If the system works ok after that then jobs a good un.
Oops, for some reason I wrongly interpreted that as a Potterton Puma. As they use the Myson pumps presumably.

To avoid any confusion I have edited my previous posting.
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Thanks for the tips Agile and 45yearsgasman. I will probably look at replacing the pump shortly.

To get rid of the black water (sludge) is powerflush necessary ? I have read that it is quite expensive and will be done when changing boilers anyway

I try not to spend too much money on this old boiler as when it fails , I will at least have some savings for a new boiler!
Remove each rad and flush them outside with mains water. That will go a long way to removing sludge as rads are where it mostly collects. A chemical flush can be done and that may be all that is required to cleanse your whole system.

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