15mm or 22mm - Grundfos Niagara 1.5 Bar pump

Hi guys,

I've a plumber coming next Monday to plumb in a shower pump. I have bought one of these:

http://www.plumbworld.co.uk/grundfos-niagara-15-bar-twin-1655-18701

All the web adverts for this pump say it is OK for use with 15mm or 22mm pipe work however when I read the manual, it says the pipework must be 22mm MINIMUM.

I have looked on numerous web sites and they all say the same - 15mm or 22mm but the handbook is clear 22mm minimum.

My plumber has said that (given the plumbing available) the best way to connect the pump is by taking a feed from the 15mm H and C supply which runs near to the cupboard in which the pump will be situated.

Do all pumps recommend 22mm in this way, when in reality 15mm is fine? Or do I need to change the pump for one which is definitely 15mm compatible.

I know what the manual says but I just wonder whether in reality it is really so important.

Thanks for any assistance!

Ed

Could be a misprint? Grundfoss web site says 15 or 22, I would contact them to clarify.

http://www.grundfos.com/web/HOMEuk.NSF/Webopslag/DMAR-7EVHZW

Thanks for the reply. I spoke to Grundfos tech Support. Apparently this is a common query as the documentation is not at all clear - they are looking to update it due to the number of calls they get. Great!

Basically, it needs 22mm on the supply but 15mm is fine on the outlet.

If you run 15mm on the supply you risk cavitation / pump damage due to lack of water supply.

I've had another think and there is a way to get 22mm on the supply so I'll get the plumber to do that. Should be better anyway as the flow should improve with 22mm.

Cheers,

Ed