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Which Boiler?

(31 Posts)
OliviaBenson Wed 24-Jul-13 18:48:48

Hi all,

I'd appreciate some advice. We live in a 3bed house with a bathroom upstairs and cloakroom downstairs. I should say its an older property and rather large as the downstairs has been extended into former outbuildings. Our boiler is 26 years old and costing us a fortune to heat the house with. It also has a hot water tank and we prefer instant hot water.

Anyway, so we are looking at either the Worcester Greenstar Classic 42CDi or Vaillant ecoTEC 838. Does anyone have any experience of these? Both have good reviews and are Which? best buys.

Its so complicated - any help will be appreciated. We had a Worcester in our last house which was great. I like it as its powerful as well. The Vaillant is slightly less powerful but it does state that it is good for older properties as it has a higher minimum heat output. The 7yr warranty is also tempting.

I think we are ok in having a combi boiler. We really want to get rid of the tank!! I have seen a Vaillant one with a tank inside the actual boiler (if I've got that right).

If you're still with me, any comments on this is welcome!

specialsubject Wed 24-Jul-13 19:44:54

Is this gas or oil? For the latter, boiler sizing is critical, too big being as bad as too small. There are calculators online which help you size up a boiler, and of course your installer should use those.

also relevant are your wall insulation, your windows, which way everything faces and many other factors.

OliviaBenson Wed 24-Jul-13 19:59:04

Its gas - ooops, should have put that. Will look out for a calculator - thanks.

Windows are being replaced in October with timber double glazed units. Walls are solid so no insulation (and are fairly thin as well). Windows to most rooms get the sun all day in summer, but not in winter as its too low and neighbours house blocks it.

I hadn't even thought of all that stuff!

CinnamonAddict Wed 24-Jul-13 20:06:43

We have the mentioned Greenstar and it's fine. High flow rate, when someone flushes loo downstairs, you don't notice it taking a shower upstairs. It will also be sufficient to put another shower in the loft.

I don't know the other one, pigletjohn will be along soon wink

OliviaBenson Wed 24-Jul-13 20:07:23

Thanks Cinnamon! That's good to have a recommendation.

morethanmama Sat 27-Jul-13 08:24:40

We had the 42. It was great. Now have most inefficient thing in world but am toying with pressurised system rather than combi.

OliviaBenson Sat 27-Jul-13 09:06:25

Thanks!! Looks like the 42 is in the lead.

PigletJohn Sat 27-Jul-13 15:56:13

I see no advantage in a higher minimum heat output. For a combi it means that when you run a hot tap, unless you are taking quite a big flow, the water will be either scalding, or cold. Modern boilers modulate their heat down to try to match demand, so a lower mininum is better.

The boilers ith an integral hot tank are better for filling a bath, as they already have a quantity of hot water ready to go. they are more expensive to run in summer as they are constant keeping this water hot. In winter you will not notice the difference.

How many bathrooms and showers have you got? How many people are likely to be running taps (hot or cold) when someone is in the shower?

Most importantly, if you fill a bucket at the kitchen sink cold tap, or the garden tap if you have one, and time it, how many litres per minute does it deliver? What happens if you turn on another mains pressure cold tap (e.g. the garden tap or possibly a utility room cold tap) and measure it again?

What colour is your incoming cold water pipe? (this not a joke)

OliviaBenson Sun 28-Jul-13 09:41:09

Thanks PigletJohn. I'm away for the weekend- will try the bucket thing tonight and get back to you. I appreciate your help!

clopper Sun 28-Jul-13 10:03:04

quick hijack here! When I put the downstairs sink tap on the water leaks out of the bath tap and shower (also terrible noise) Is this likely to be boiler related?

PigletJohn Sun 28-Jul-13 19:35:53


you actually mean it comes out of the taps? Is it more than a cupful?

is it just the cold taps? are they at mains pressure? are they mixers?

hammering noise or droning noise?

how old are your pipes?

OliviaBenson Mon 29-Jul-13 12:48:59

Hi PigletJohn.

Just timed the water- its about 15-16 seconds per litre. This reduces down to 17-18 when another tap is on.

There are two of us here- only one bathroom but there is a downstairs cloakroom. Dh tends to avoid using water when I'm in shower and vice versa.

It's interesting what you say about the minimum heat output for water- the Valiant website and Which? both say that a higher minimum is more suitable for larger/older properties.

House is about 150sqm in total (if that's useful). No idea where the feed comes into the house- could you suggest what I'm looking for (sorry! I've just got no idea!)


PigletJohn Mon 29-Jul-13 13:32:32

4 litres per minute is very poor and will be inadequate for a combi.

A higher maximum makes sense. Not a higher minimum

You are looking for the pipe that comes into your main stopcock. It is very often close to the kitchen sink.

Every householder needs to know where the main stopcock is because it is what you turn off when you have a leak or burst pipe, or if the house is left empty, or unheated in winter.

A stopcock has a "T" handle not a round one. It is also a unique shape (note the diagonal slope on the "out" side. They are usually brass.

Some modern houses with plastic incoming pipes may have a large plastic stopcock, often blue, that looks different.

If you cannot operate yours by hand, get a special tool to turn it, and work it to and from before the emergency occurs. Never wind it all the way open, turn it right to the end, then back a turn. This reduces the risk of it jamming. It might drip a bit from the spindle, this can easily be fixed.

PigletJohn Mon 29-Jul-13 13:39:32


can you give me a link to the pages about Minimum output please

PigletJohn Mon 29-Jul-13 13:52:39


I had a look at Which for the 838. The higher minimum they are referring to is for the Central Heating output, I thought you meant for hot water. In fact I don't agree with them, beacause, even a large old house, once it is up to tempeature or if the winter is mild, will have quite a low demand for heat. My own boiler modulates between 8kW and 30kW depending on demand. and most of the time it runs at quite low output (so is quieter and produces less steam, also it does not have to turn itself on and off frequently, which would be uneconomical). IMO it would be more accurate to say "it has quite a high minimum output which is not so bad for a large or old house."

It also says it can deliver 15.2 lites of hot water; but if your supply pipe only provides 4 litres per minute from the mains, this boiler is not much use to you.

It may be possible to run a new, larger water pipe from the pavement, which will improve flow a lot, unless perhaps you live in a remote area with a poor water main. It will involve digging a trench. Or there might be a restriction inside your house that could be corrected.

OliviaBenson Mon 29-Jul-13 14:00:06

Right, had a search and the stopcock is in our cellar (in my defence We haven't lived here long - still no excuse though!). It looks like the one you linked to. The pipe feeding into it is lagged, but having a peak, it looks metal, matching the stopcock if that makes sense. It isn't a particular colour other than metal.

I did think our pressure was rubbish but our plumber thought we'd be ok with a combi. Is there no chance at all?

I'm a member of Which? so can't link directly as you will have to sign in. For the Valiant, I have copied this from there:

"Central heating output: 11.2 to 30kW; the high maximum output ensures that this boiler is powerful enough to heat cold radiators up quickly and cope with colder weather. But the minimum heat output is quite high, so may be overpowered for very well-insulated homes with few radiators."

I realise now though that its about the central heating rather than water blush apologies.

Would the Valient ecoTech Plus 937 work? That's the one with the inbuilt tank. We were trying to avoid the tank route as hate heating up water in tank (much prefer on-demand) but I realise this may be an issue.

Thanks for your help - really appreciated.

OliviaBenson Mon 29-Jul-13 14:02:07

Cross posts there! We live in a town. Who would do the digging, would the waterboard need to do it?


PigletJohn Mon 29-Jul-13 14:03:37

grey pipe and not very straight (may have bulbous joints or hang in droopy festoons) is lead

rusty or painted, very straight, is steel

penny-coloured is copper

black is plastic

blue is plastic

OliviaBenson Mon 29-Jul-13 14:06:09

Steel (could feel some rust behind the lagging!)

PigletJohn Mon 29-Jul-13 14:17:10

1) the digging: You, or your plumber (or more likely a labourer working for the plumber) would dig it. The water company won't care, except that if your supply pipe is leaking, or is lead, they may have a replacement subsidy scheme. If the new pipe is joined inside your boundary, your plumber does it. If joined to the main uder the pavement, they do it and charge you for digging a hole. It wil be easier if there is a meter, or you contrive to have one fitted after you have got your new pipe in place. They will inspect your new pipe to assure that it is deep enough not to freeze. They will have a register of approved contractors who can do it. They may possibly have their own minor works department who will do it for a price.

If you are going to the troube of having a new pipe laid, have at least 25mm plastic, preferably 32mm. The cost of pipe is trivial compared to the cost of laying it. It is easier if you have a frond garden or gravel, than if you have an expanse of concrete. It is easer to lay in teh space under wooden floors than to dig up concrete floors. The new pipe does not have rto folow the same route as the old pipe.

2) the boiler: A combi boiler with its own hot-water storage will not output water from the taps any faster than the new water from the main comes in. Only a cold water tank in the loft can deliver water faster from the taps than is supplied from the main.

3) the pipe: Is it about an inch external diameter? Is the stopcock turned fully on (except for half a turn?) Don't worry if it makes the pipes noisy when fully open, that's a differernt matter and can be fixed

OliviaBenson Mon 29-Jul-13 14:25:56


We have a meter but its on our drive, so I guess the plumber will do it. Its all concrete though so this could be more costly that thought! No easy way to get around it either, from what I can see.

2) - fair point!! Makes sense when you point it out. We have an existing cold water tank but rather than it being in the loft, its in our bathroom, above the hot water tank.

3) It is about an inch yes. I'm not sure if the stopcock is fully turned on - I can't move it. Will get my DH to try this evening. Fingers crossed it isn't fully on - it might increase the flow rate!

PigletJohn Mon 29-Jul-13 14:31:06

stopcock key from a place that sells plumbing stuff. the "crutch" fits over the T handle. If it is fixed to steel pipe it will take quite a lot of gorce (lead or plastic pipes can bend or tear unless the stopcock is clamped rigid)

there are much longer ones for operating stopcocks that are buried with a small trapdoor cover at ground level and a deep access pit.

Turn it to and from a tiny amount at first, slowly increasing the turn amount.

PigletJohn Mon 29-Jul-13 14:31:38

force not gorce.

OliviaBenson Mon 29-Jul-13 14:51:06


OliviaBenson Mon 29-Jul-13 19:50:18

Tried the stopcock. Turned it off and opened it up, no difference to pressure. sad

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