Is my plumber exagerating?

[JavaEnquirer]

Hi. I've just had a quote from a plumber for a new gas boiler. I don't understand much about the ins and outs of central heating, so apologies for any vagueness.

We have an old gravity fed system which we wish to replace with a combi. He told us the tanks need to come out, some earthing work is required and the total price for labour and the boiler is =A31760. ( It seems he has a fixed price ) The boiler is a Baxi and that alone will account for =A31050 of the =A31760. I believe he said it was a 80,000 btu boiler. It will also be powering 11 radiators in a small traditional victorian terrace.

This is the crux, is this claim he made true: "Hot water pressure will be close to mains cold pressure. You'll have a great shower with a heat regulator, so the heat and pressure will be constant even when the heating is on or whatever." To demonstrate, he turned on a cold and a hot water tap ( from existing tank ) and said the pressure would be somewhere between the two in the new system.

The shower and labour would cost an additional =A3190. From what friends with combis tell me, I was under the impression that the heat output from the shower would jump all over the place as people turn on and off taps elsewhere in the house. I had been planning on a 10.8kw electric shower, but he said it was pointless.

Also, he recommended the radiators be changed as they are 20-30 years old. He said he could flush them out with chemicals, but it wasn't ideal. Without measuring, he quoted roughly =A31000 for the new radiators and installation.

Many thanks in advance. Any advice is greatly appreciated. Cheers.

[JavaEnquirer]

oops. I forgot. The boiler will be on the groundfloor and the shower will be upstairs.

[Stu]

What you want is a thermostatic mixer shower. We have one on our combi and its great, constant temperature with good pressure and flow.

[Fitz]

total price for labour and the boiler is =A31760. ( It

I'm by no means an expert but that doesn't sound excessive.

It's fairly simplified but basically true. The crucial thing to note is that the bolier will have a maximum throughput limited by the power of the boiler. Once the mains pressure is higher than that throughput the boiler becomes the limiting factor. The higher the mains pressure the less interference there will be with the boiler output when using other taps.

If you use a standard shower mixer then yes this will happen. If you use a thermostatic shower mixer then no you'll be fine. You may still experience a pressure drop at the shower but the mixer should cope with this and adjust the temperature so you get a briefly weaker shower that doesn't scald/freeze you. Then once the tap use has finished it'll come back up to full pressure.

There are some arguments for electric showers e.g. it's a source of hot water if the gas goes. But given the infrequency with which this happens you should really avoid them if there is an alternative. The

10.8kw will just about give enough water to function as a shower but it's not a very nice shower experience. Someting often overlooked as well is that you have to route a chunking great big cable from the consumer unit to the shower which in itself can be costly. If you get a combi then use it for the shower with a thermostatic mixer.

I'll leave this for the more experienced, but again it doesn't sound excessive to me...

Of course remember to get proper fixed quotes not just estimates.

--=20 Steve Fitzhugh

[Mark Hewitt]

Sounds about right, in fact it looks like you are getting the boiler somewhat cheap. Although Baxi is at the budget end of the range. Take a look at the flow rates in terms of litres per minute. Our installer offered us a choice of 5 from about £1,100 to £1,700

Yes absolutely, that's the great thing the hot water comes out at near mains pressure so showers are fantastic compared to gravity systems. However if someone else turns on a tap in the house the flow across both the hot and cold will decrease substanitally.You *need* to have thermostatic control on your shower.

Sounds reasonable.

The heat should not, the most that should happen is that your flow will decrease. Your friends may not have good thermostatic controls.

Good advice. No good running a new system with creaky old rads. New ones are far better too.

Get a quote from at least three installers.

[Mark Hewitt]

No problem, my girlfriends house is like that and it's great, the only problem is that sometimes the hot water takes a while (about 1-2 minutes) to come through properly.

[Roger Mills (aka Set Square)]

What your plumber says about combis is broadly true on a good day with a following wind!

Combis are fed with mains pressure cold water - which they heat up on the way through, so it comes out close to mains pressure - except that they usually need to restrict the flow in order to achieve an adequate output temperature. [The faster the water flows through, the less it gets heated].

80,000 BTU is about 23.5kW in real money - so it's over twice as powerful as the most powerful electric shower - but *all* electric showers are pathetic, anyway! 23.5kW will heat up your house nicely, and will give you an adequate shower *provided* it has a decent flow/temperature control system (some do and some don't!) and provided your mains cold supply is adequate.

See if you can get your plumber to negotiate with one of his previous customers with the same system for you to try out their shower - then you'll see for yourself before committing yourself. Also, measure your cold flow rate at the kitchen tap with a bucket and stopwatch. It needs to be at least

20 litres/minute.

If any members of the family bath rather than shower, it will take a very long time to fill the bath with hot water compared with your existing system. You should be looking at at least 30kW - and even that would be slow compared with a stored hot water system.

[Lunny]

Why not find out the model of the boiler and shop around on the internet for it? If you find it cheaper tell him you'll get it yourself. Why should he be bothered he's just supplying it after all.

I did this with a recent CH installation quote and was surprised that I could reduce the materials from about =A32000 to =A31500 by buying online. They were good quality components too.

[Dave Plowman (News)]

If the plumber fits bits bought by yourself, he's under no obligation to fix for free if things go wrong within say a year or so.

[The Natural Philosopher]

Just my 2c worth.

Going mains pressure is a huge step up on shower experience, BUT as others have pointed out,you need a lot of peak power OR some heats storage device to get even ONE shower working well, and while it is, a combi will not be doing any house heating.

And as for two showers - well you may need a 30KW plus boiler for that.

You have to balance the cost of THAT option, against the other alternative - mains pressure boiler and pressurized hot water tank.

I have a n bathroom 5-6 bedroom house and that functions entirely of a

15KW boiler. Small and cheap. The hot water tank of course is large and nearly as expensive :-)

It does have the advantage that if you run out of oil or gas, you can still use the immersion heater to heat the tank and have a shower :-)

I would say the combi scores in a smaller house with one or two bathrooms..and where space is at a premium...once the house gets larger or has more bathrooms (loads of teenage kids?) a system boiler and hot water tank is actually a far better option and no more expensive.

Take the time to understand the issues and costs, rather than go with the religion you will find here, and make up your own mind

I think we are probably all agreed that a cold water header tank and low pressure water, or electric showers or a booster pump is the worst of all possible worlds.

[Lunny]

He's under no obligation but a boiler costing you =A31050 should be costing the plumber =A31050 so if you can get the exact same thing cheaper why should he wan't to be funny about it?

Perhaps you could ask the plumber to buy the components from the place of your choosing. If he won't do that then find out where he's getting them from and check the prices direct. If he won't let you do that then I'd find another plumber.

I suspect that my plumber could easily get the materials for =A31500, it was just that he was quoting me =A32000 for some reason......It's not uncommon for some tradesmen to pay trade prices for materials and charge the customer retail prices.

[Roger Mills (aka Set Square)]

I would agree with the electric shower bit - but there's now't wrong with a gravity-fed hot water storage system with a shower booster pump.

[Doctor Drivel]

There is a lot wrong with it.

[Mark Hewitt]

Such as?

[Doctor Drivel]

dirt in tank rodents in tank Enviroment rife for Legionella space consumed by and tank in small British homes space consumed by cylinder in small British homes Lots of pipes to freeze. Pathetic showers because of low pressure Need a noisy, expensive, leaky power shower pump Separet boiler taking up space needed. etc,

Best avoided if possible.

[.]

seems reasonable, except for teh rads - seems a bit on the high side.

/however/

c£2600 + shower for a new system in an /occupied house/ ? go for it but see if you can get a glow worm boiler instead, similar price but they run almost silent. don't forget the tea and bacon sarnies every lunchtime, saves them from going off site ;-)

[Doctor Drivel]

We have an old gravity fed system which we wish to replace with a combi. He told us the tanks need to come out, some earthing work is required and the total price for labour and the boiler is £1760. ( It seems he has a fixed price ) The boiler is a Baxi and that alone will account for £1050 of the £1760. I believe he said it was a 80,000 btu boiler. It will also be powering 11 radiators in a small traditional victorian terrace.

This is the crux, is this claim he made true: "Hot water pressure will be close to mains cold pressure.

You'll have a great shower with a heat regulator, so the heat and pressure will be constant even when the heating is on or whatever."

To demonstrate, he turned on a cold and a hot water tap ( from existing tank ) and said the pressure would be somewhere between the two in the new system.

The shower and labour would cost an additional £190. From what friends with combis tell me, I was under the impression that the heat output from the shower would jump all over the place as people turn on and off taps elsewhere in the house. I had been planning on a 10.8kw electric shower, but he said it was pointless.

He is right. Make sure he has one dedicated pipe from the stoptap to the combi inlet and nothing teed off this. Tee off the cold to the shower just before the combi odd this dedicated cold feed pipe (the only tee). Have all the cold outlets off the one pipe from the stopcock.

Also, he recommended the radiators be changed as they are 20-30 years old. He said he could flush them out with chemicals, but it wasn't ideal. Without measuring, he quoted roughly £1000 for the new radiators and installation.

Many thanks in advance. Any advice is greatly appreciated. Cheers.

[Doctor Drivel]

Nonsense.Even the smallest combi gives a v good shower.

You mean an unvented cylinder. Avoid as they require an annual service that costs. They can also blow up.

Best go for a thermal store or Heat bank.

[Dave Plowman (News)]

Because he's quoting you an inclusive price to supply and fit. If you decide to try and source even an identical make from elsewhere and get him to install it it's still your risk. What happens if it arrives damaged, for example? Should he absorb the time wasted?

So he's got to travel perhaps miles to save *you* money? Or arrange for delivery from a supplier he doesn't normally use?

Whilst this is true, it's all part of the inclusive price. Try and reduce his 'profit' in one area and he likely won't want to know.

Either DIY the job, or get the best price from a pro. There are plenty out there. How the price breaks down isn't an issue.

[Dave Plowman (News)]

Or without with a reasonable head. Some prefer a high flow moderate pressure shower to a low flow high pressure type. It gets you clean quicker. ;-)