Hot water circulation pumps

[Raymundo]

Hi all,

A friend has a Grundfos UP20-15N pump to circulate the hot water and save wasting water while waiting for the hot stuff to arrive. Well, the pump failed and, when we opened it, we found the plastic impeller seized solid in the stainless housing. It's gunged up solid and impossible to free, so a new pump or head is needed - and thy ain't cheap! The question is, couldn't a standard CH pump do the job? Even if it only lasted a few years, it would be a lot cheaper than the original, which failed anyway. Any advice would be very welcome.

Raymundo

 

[stem]

I believe it's because the constant supply of fresh (oxygenated) water would cause corrosion problems for a standard circulator as used for central heating.

In central heating systems because the same water is circulating continually much of the oxygen in it is lost, also usually an anticorrosion agent is added.

The circulators for a 'circulation ring' to provide domestic hot water to the taps are made from bronze (or stainless steel) and plastic to prevent corrosion.

 

[Biggles..]

It's because the one used for hot water is stainless or bronze(older ones),a ch pump isn't and is therefore unsuitable under WRAS.

 

[Raymundo]

Thanks for the replies, Gents.
I still find it hard to see the point of stainless-steel and plastic parts if you're in a hard-water area. This pump is gunged up solid - the rotor couldn't be dug out of the casing without getting broken. This made me wonder if cheap shower-pumps are all-plastic, or do they use stainless? £240 (minimum) for a replacement, which is basically a CH-pump with a SS insert seems an awful lot if it still gets seized!

Raymundo

 

[Onetap]

Was there a non-return valve on the return connection?

Did you try dissolving the limescale with de-scaling solution?

 

[DeltaT2]

We use Lowara secondary return pumps. Cheap as chips.

 

[flameport]

Thanks for the replies, Gents.
I still find it hard to see the point of stainless-steel and plastic parts if you're in a hard-water area

The main point is they don't corrode, which would result in rusty water coming out of your taps.