To Vent or Not to Vent!!

16 Sep 2004
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United Kingdom
I have a Wbosch system boiler with an indirect vented cylinder. I'm considering installing an unvented cylinder (santon/albion) to improve my DHW pressure. The problem I have is that my cold mains is entirely piped in 15mm copper (to replace this with 22mm would be too costly/disruptive). Severn Trent have advised that the cold water pressure should be a minimum of 1.5 bar. I have measured the flow rate at about 12 litres/minute. It would seem that my cold water pressure/flow are not sufficient for an unvented cylinder- do pple agree?

As an alternative I have considered fitting a pump to the DHW pipe (22mm) just as it exits the current vented cylinder (perhaps a stuart turner single 2.0 bar monsoon).

What would YOU choose?!
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You need at least 3 bar for an unvented cylinder and a heafty flow rate too. If you pump water, you need to work out how much storage you need for how much time you have the water on at whatever flow rate. More modest demands on your water supply would make life easier.
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I fitted a combi boiler years ago on a farm he only had a spring at the top of one of his fields i diverted the spring into a holding tank and pumped it to the boiler worked ace, so you can get round any situation and no im not going to do it for you

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