Can we fit a combi boiler?

[TreaterAnita]

Our boiler has just given up the ghost. This is not unexpected as we inherited it when we bought the house a couple of years ago and it's clearly pretty ancient. We've decided to replace it rather than attempting to fix it because we currently have no way of heating water without having the central heating on (no immersion heater for the water tank) and while we turn the radiators off in summer, it still seems to be very expensive.

In our previous house we had a combi boiler which we much preferred for the instant hot water and we'd like to fit one of these (appreciating that this will require a bit of replumbing). However our water pressure is pretty low. I've measured it at the kitchen tap before and it's just above the minimum that the water authority is required to supply. Does anyone know if that will prevent us from fitting a combi boiler and, if so, what the alternatives would be that would give us instant (or at least quick) access to hot water?

What made you choose a combi? What colour is your hot water cylinder? Doesn't it have a 3-inch boss for an immersion heater on the top or side?

How many people live in the house?

How many baths and showers are there?

Run the cold kitchen tap into a bucket. Time it to full. How many litres per minute does it give? Is it the same in your garden tap and utility room (if any?)

How many lpm come from the hot bath tap, and from the cold bath tap?

Thanks for replying PigletJohn, I was hoping you would!

To answer your questions:

• We chose a combi last time I think on the recommendation of the plumber - we didn't have any water pressure problems in our old house though.

• The hot water tank is copper and there is also a smaller black plastic tank which is presumably a cold water tank.

• I'm not entirely sure what a 3 inch boss for an immersion heater would look like, but I can't see anything that would seem to be a likely suspect.

• There are 4 of us in the house - 2 adults and 2 children.

• We currently have 1 bathroom with a shower/bath. Plan is to convert the attic in the future and install a small ensuite up there - hence it would be good to do away with the water tanks if possible, though I suppose that we could work around them if necessary.

• Kitchen cold water tap gives 9 litres/minute, as does garden tap.

• Hot water tap in the bath gives 16 litres/minute and cold water tap gives 14 litres/minute.

We've had 2 engineers out today. The first one (small firm) said we'd be fine with a combi boiler and gave us a quote to fit it, including moving it out to the garage. Second one (British Gas) said that our water pressure was too low for a combi and he'd stick with the system we've got - so pretty confusing!

A lot of my ramblings are on another thread

If the 9 litres per minute is the flow from the watermain, and your bathroom hot and cold taps are both supplied from the cold water tank in the loft, then you will get very poor results from a combi or an unvented cylinder. Your loft bathroom will be very poor whatever you do. You could have a shower pump and a cold water tank; it will be a bit noisy.

Consider having a new water supply piper run out to the main or meter under the pavement, in new, larger, plastic pipe. This will almost always dramatically improve the flow, and you could then get good results from a combi or an unvented cylinder, and would not need a loft tank. This is a fairly common improvement for older houses, especially if the have half-inch lead or iron pipes which are at the end of their life and give a very restricted flow. If your house is close to the road and a trench can bed dug through a flowerbed, it may only cost a few £hundred. If it is a long way or involves excavating or moling under concrete, it may be thousands. The new pipe does not have to follow the same route as the old one. If you have lead pipes you might get a lead replacement subsidy.

Plumbers can lay the pipe but are often frail, weedy fellows with petal-soft hands so you may need a labourer or small builder to dig the trench, or possibly a sturdy gardener. The water company will inspect it before connecting. It must be 450mm or more deep.

That's brilliant advice, thank you. My dad came round earlier and checked the pressure which was actually 3 bar (which I think is 3 x the minimum) and so we've spoken to the neighbours who confirmed that pretty much everyone on the road apart from us has had their water supply pipe replaced and it's massively increased the flow rate. We do have lead pipe so our utility company will replace their part and connect us for free and my dad is going to do our section (he's a builder) and then we can have a combi boiler and a decent water supply - hurrah!

hooray hooray!

Ask your water company to test your drinking water for lead content, and see if they offer a lead replacement subsidy. The test has to be done before you start work so ask straight away in case they are slow making an appointment.

I'd suggest a 32mm plastic pipe with full-bore valves. It is only marginally more expensive than 25mm pipe and the labour is the same. It is a bit over-generous, but I like that. If you are thinking of having two bathrooms in future, consider an unvented cylinder and ask your installers what they think.

Great advice from Pigletjohn ??
Just to add, an Unvented cylinder, combined with a system boiler will do away with all the tanks in the loft. If, after the water supply has been increased you still don't have enough flow an Accumulator can be installed with the Unvented, though it is almost the same size as a cylinder, so if space is of a premium this may not be an option.