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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!

PigletJohn Thu 01-Aug-13 13:30:26

heat only system boiler with an unvented cylinder
is a good modern solution, provided that you have a good flow of water into the house, which is mostly dependent on the incoming service pipe. It would be no good with your current weedy flow.

20 litres per minute is good.

12 litres per minute is not good, but is usually adequate unless you want to run two showers at the same time.

Note that I say flow which is not the same as pressure. You can get high pressure out of a hypodermic syringe but it would take weeks to fill a bath.

OliviaBenson Thu 01-Aug-13 08:52:16

Sooooo, plumber came around last night. He thinks the steel pipes might be furred up from the inside which might be affecting pressure. He is going to check the pressure from the feed into the house today.

He suggested a heat only system boiler with an unvented cylinder if it is a general pressure issue and not something going on in the house.

We shall see....

PigletJohn Tue 30-Jul-13 22:57:33

so have I, but they are not very common, so you need to be sure you have a good local Approved Installer who is experienced on them. I am near a small town, the local firm closed down and the nearest one is now in the next-but-one town.

Mine is not a combi, so it is a simpler appliance and has less to go wrong. I chose it because of the stainless steel heat exchanger which I believe will have a long life, and opinions by trade contacts.

Spelled Viessmann.

takeaway2 Tue 30-Jul-13 06:26:12

We've got a veismann boiler and it's really good!

OliviaBenson Tue 30-Jul-13 05:53:04

Thanks- will have a look. Plumber is coming out tomorrow to have a look. Thanks for all your help.

PigletJohn Mon 29-Jul-13 23:09:06

with such a poor flow, unless you are living somewhere isolated, there must be an obstruction somewhere.

Look in the water meter pit. There are a few makes, but the sort I have used has a blue plastic T handle to one side of the meter, which turns the water on and off. Confirm it is fuly open. If you pull up it will come off but can be pushed back on. Also look to make sure the bubble is not spinning when all your taps are off (this would indicate a leak)

Before digging your trench, find a plumber and ask them to take the outlet pipe off the stopcock, and put a test pipe on so you can verify the flow into the bucket (this is in case the obstruction is somewhere in your house)

old lead pipes are more often obstructed, as they are soft and can get squashed underground.

A old experienced local plumber will have more ideas about what the trouble could be (e.g. rust inside the pipes; poor water main, an additional stopcock hidden away) in your area.

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

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

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


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

force not gorce.

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.

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 14:17:10

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 14:06:09

Steel (could feel some rust behind the lagging!)

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 14:02:07

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


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.

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.

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 13:32:32

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.

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 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?

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?

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!

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 Sat 27-Jul-13 09:06:25

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

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