Domestic Solar waterheating pump problem.

[watford 99]

My solar hot water system pump keeps stopping. I am able to restart the pump by turning the shaft but it is not long before it seizes up again. I guess this means the system needs flushing, new glycol put in and,maybe, a new pump installed. Having changed central heating pumps in the past I would like to do the work myself to keep the cost down. I guess I will need to buy a pressure bottle and glycol. However I would really appreciate any advice as to how I should go about emptying, flushing and re-filling the system avoiding air locks. There is a short threaded outlet pipe, controlled by a service valve, integral with a site glass and positioned just under the pump. There is also the usual pressure vessel and safety valve. The system has 20 glass tubes on the bungalow roof.

[Drawmer]

Has the pump got isolating valves either side of it?

If so, just close them off, replace the pump, top up with a bit more glycol, and off you go.

Not sure why you'd need to flush the system - do you have any evidence that there's contamination, or has the existing anti freeze/inhibitor ceased to work?

I made an 'injector pump' to fill my system from a garden sprayer, which had already been modified to make it suitable for refilling reluctant kit car cooling systems!

Hopefully, you'll get some more informed advice regarding the longevity of the heat transfer liquid soon.

[watford 99]

Paul
Many thanks for your answer. I do not know how long the glycol mix should last though I think I have read 20 years. Also, I do not know how old my system is as it was already installed when we moved here which was late in 2007. I believe the system may only have been installed a 2 or 3 years prior to then so it is not very old. I was thinking that the glycol mix might have sludged up and his was causing the pump to seize. Hence my idea of doing a flush and refill.
The temperature at the collector seems to reach 140 degrees C. or higher, especially when the pump stops, and I do not know if this has a detrimental effect on the glycol. I would welcome any information from others who may be experienced in these matters. Modifying a garden pump up spray bottle to connect to plumbing fittings might not be too easy unless someone who as done it can explain how.