My latest house has the old-style header tank which I’d like to change for mans pressure. Is my main concern the hot water cylinder that will need changing for a megaflo type? I’m assuming the boiler is at least notionally capable as it looks to be exactly the same make and model as the one I had in Scotland running mains pressure. Before I try to persuade a plumber to come and look, is there anything I’m missing? I changed the house in Cambridge to mains but that was part of a combi boiler job. We sprung a few leaks in pitted pipes but that was all.

As I understand it if you have a header tank which is operational then your boiler is pretty old and I'd venture due a change. A combi boiler as such, again as I understand it, operates on a sealed, pressurised system, and any drop in pressure can be topped up by opening the dedicated mains valve temporarily to top it up - the dial to measure this by being easily visible on the appliance.

These days the favoured type are condensing boilers which are a bit dearer (of course) but more efficient.

There seem to be two options of the above, one allowing hot water to come directly from the tap (therefore mains pressure) and the other is a "system" which incorporates a hot water cylinder for storage of hot water. These I think may also be installed with an electric element to provide an alternative source of powering your water heating. The former option does away with header tank, h/w cylinder and cold water storage tank.

Now that Reuben has been "found" I'm sure he'll be on to put the pro's view

I don’t think the boiler is “too” old - as I say, it looks identical to the one in Scotland (10 years old - ish). The house is “too big” for a combi boiler. It’s oil-fired too.

As for condenser boilers, the guy who did the energy certificate for my Scottish place said they were only marginally more efficient - judging by the savings predicted on the cert, I think he is right.

we have the type of arrangement I think you are looking for. Normal boiler. pressurised hot water cylinder with a couple of pressure vessel. No c/w or c/h header tanks.

I don’t think you need a mega flow tank - you may be able to use your existing tank or if not use a new normal tank.

How high is the mains pressure? At our house it was marginal (a bit low) when the water was flowing so we have a "bladder" vessel in the loft that uses the static pressure (mains pressure when not flowing) to store pressure in the bladder and provide higher pressure cold water. This was added as part of a recent extension to provide water to an extra en suite and heating in an attic room, we got rid of the cold water tank and small hot water top-up tank in the loft and replaced the hot water cylinder / immersion heater with a massive great hot water tank, plus put the bladder tank in one corner of the loft, and there is some other little pressure vessel near the new boiler. I had a hard time understanding the simple CH+HW plumbing we had before, now it's even more complicated It was not cheap either, wouldn't you be better off adding a dedicated shower pump if that's the only issue?

Due to high pressure coming in from our mains I have fitted a reducing valve set at just under 3bar.

I imagine the heating engineer will fit one for safety . But as you know I do live in a different country.

DaveG the “bladder” tank will most likely be a pressure/expansion vessel same as the one by the boiler. They are there to allow for the pressure changes in the CH and HW systems. It can’t really store any pressure for future use.

Oh and to add the pressure vessels also help reduce any issues with pump surges.

I have a single shower pump but I need another and I don't much like the noise they make. I could fit a single bigger pump but it also feels wrong to me to knock the pressure out of the water then pay to put it back in.

Before our major re-plumb we had a pumped shower but the pump was in the loft and you couldn't hear it. But consider the cost of another shower pump vs. a complete system revamp...

Yup - I’m hoping that it will just be a different water cylinder and some pipe work simplification rather than a system revamp

Yes it’s pretty simple from what I remember on ours. Just linking the rising main back to the tank outlet - capping off anything else. I would suggest putting the pressure vessels where they are accessible as they don’t last forever and/ or need recharging with air from time to time - or ours have at least.

Basically you wanted an unvented cylinder fitted.
Your boiler won’t be affteted as you are simply changing the design of the HW circuit. Heating circuit doesn’t change just some repiping to the new cylinder and a bit of wiring to its new thermostat etc.
Dependant on the cylinder the simple premise is a new cylinder, main pressure reducing valve,pressure relief and expansion vessel.

This is notifiable for building regs and the engineer has to be qualified to work on unvented cylinders as in affect they are a pressure bomb. Maybe slightly different in Scotland although.

Cool - I will investigate. Thank you.

One more thing. Remember that the water company (Thames?) can and probably will reduce pressure at some point which might reduce the benefit of a main pressure system. it really depends on what you pressure is and where you sit in the system.

Just a heads up really - not much you can do about it.

Thanks. The pressure seems very good now (hence my thoughts). We have Wessex water who, so far, I rate. They did charge me £111 for my first two months (half of which I wasn’t here), billing me for 26m3 of water. But a quick call and check of my meter and they say they must have cocked up their opening reading and will sort it based on my usage over the next month.