WJM Posted January 25, 2018 Report Share Posted January 25, 2018 I need to change my central heating circulation pump. The boat, and therefore the liquid in the system, is 11 years old now. Should I drain the system and refill with new liquid? Or is it better left as it is? If I do replace it, I presume it needs water mixed with anti-freeze? Should I use car type anti-freeze or a special type? Link to comment Share on other sites More sharing options...
Psycloud Posted January 25, 2018 Report Share Posted January 25, 2018 https://www.screwfix.com/p/no-nonsense-central-heating-inhibited-anti-freeze-5ltr/74586 is what I used Link to comment Share on other sites More sharing options...
BWM Posted January 25, 2018 Report Share Posted January 25, 2018 (edited) If it's 11 years old you may want to refill with water after changing the pump, run for a couple of hours and then empty again to flush the system-and will enable you to check for leaks without wasting antifreeze. A decent corrosion inhibitor would be a worthwhile addition. Edited January 25, 2018 by BWM Link to comment Share on other sites More sharing options...
Tonka Posted January 25, 2018 Report Share Posted January 25, 2018 Fernox Alphi available from plumbnation. much cheaper then screwfix Link to comment Share on other sites More sharing options...
Slim Posted January 25, 2018 Report Share Posted January 25, 2018 14 minutes ago, Tonka said: Fernox Alphi available from plumbnation. much cheaper then screwfix Interesting. I just googied Fernox Alpha at Plumbnation and it's about £33 for 5 litres (didn't note VAT or dilution rate] Link to comment Share on other sites More sharing options...
WJM Posted January 25, 2018 Author Report Share Posted January 25, 2018 Thanks for the response - another question; very roughly... a back boiler, three radiators and a hot water coil: how much fluid is likely to be in the system? Link to comment Share on other sites More sharing options...
Tonka Posted January 25, 2018 Report Share Posted January 25, 2018 19 minutes ago, Slim said: Interesting. I just googied Fernox Alpha at Plumbnation and it's about £33 for 5 litres (didn't note VAT or dilution rate] 25% Link to comment Share on other sites More sharing options...
Tony Brooks Posted January 25, 2018 Report Share Posted January 25, 2018 30 minutes ago, WJM said: Thanks for the response - another question; very roughly... a back boiler, three radiators and a hot water coil: how much fluid is likely to be in the system? Size of radiators, size of back boiler, length and diameter of pipework and then someone may be bothered to work it out for you. Without those dimensions there is no way to get an accurate answer. All boats differ. When you drain it measuring what comes out is probably the easiest way. Link to comment Share on other sites More sharing options...
ditchcrawler Posted January 25, 2018 Report Share Posted January 25, 2018 8 minutes ago, Tony Brooks said: Size of radiators, size of back boiler, length and diameter of pipework and then someone may be bothered to work it out for you. Without those dimensions there is no way to get an accurate answer. All boats differ. When you drain it measuring what comes out is probably the easiest way. Plus header tank. I dont know if radiator manufacturers quote their capacity Link to comment Share on other sites More sharing options...
Tonka Posted January 25, 2018 Report Share Posted January 25, 2018 got a feeling that if you do a forum search this has been raised before. Certainly when I bought my Fernox Alphi in Nov-Dec 17 it was cheaper there then Screwfix. At the moment Plumbworld are the cheapest. Link to comment Share on other sites More sharing options...
cuthound Posted January 25, 2018 Report Share Posted January 25, 2018 (edited) I used at 25% mix of Ford Longlife antifreeze in the CH system and the engine. Lasts 10 years, making a messy job an infrequent one. Edited January 25, 2018 by cuthound Spillung Link to comment Share on other sites More sharing options...
David Mack Posted January 25, 2018 Report Share Posted January 25, 2018 And as antifreeze is poisonous, presumably the old coolant should be properly disposed of and not just pumped out into the canal. So you will need a few suitable containers. Link to comment Share on other sites More sharing options...
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