"If your water heater is working OK, is not too old and has no electrics, then there's no reason why it should not go safely on for a while yet, or at least be repairable.
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The hot water boiler in the bathroom is very new. I'm guessing it was installed when the previous owners re-developed, which was about 3 years ago.
"You're happy to have 'avoided' a condensing combi in the living room. Well OK - but what are your best long-term economic alternatives? You still have to decide what your replacement boiler will be and given the age and probable condition of the rads and pipes, your options might easily turn out to be 'New boiler now, new rads and pipes real soon!'.
I reckon I'll be in the house for about 7 more years. Some plumbers say old systems can handle modern boilers, others warn of impending doom. As my hot water boiler is an instant heat type, I'm already saving energy there, so I don't think the energy savings that I'll make annually with a condensing boiler justify the cost. The 1 quoter I had, said that the pipes would pop due to the increased pressue of the condensing boiler, but respondents on here have pointed out that I can get an open vented boiler which is under the same pressue. As there's no apparant consensus on this, I'd plump for the cheaper option. Can you explain why I'd need to replace all the pipework. I'd imagine that leaks would appear at the weakest point which would be the radiator valves? I'm not as bothered about replacing radiators, getting TRVs, room thermostat etc. but it's the replacement of the pipework which costs the hassle. Other cost savings that I make are the cost of the boiler, and the installation cost, as well as the ongoing maintenance costs. Apparantly condensing boilers are less reliable than ordinary boilers, and as they're more complex, common sense would suggest that this is true.
"As far as your information reveals, your only objections to a condensing system boiler appear to be: pluming from the flue, lack of condensate drain options (in my experience, for a ground-floor installation, if you can fit an external flue you can usually dig a condensate soakaway below it!) And as has been pointed out, not all condensing boilers demand a pressurised system - although pressurised is better technically.
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I'm only going with what the guidelines say. They warn that the plume shouldn't obstruct walkways or patios, should be 2.5m away from a boundary etc. It creates a picture of my house looking like steamboat willy blasting unsuspecting pedestrians who pass by on the pavement. Again the guidelines set mininum standards for the location of the soakaway.
If the original plumber hadn't got a bit greedy and tried to flog me a whole new central heating system, then I probably wouldn't have done so much research in to this subject.