Combi, Combi-storage or Seperate Boiler & Storage Tank

[getcarter]

After a plethora of plumbers visiting our house to quote (or not too bother quoting in some circumstances!) on replacing our half dead boiler, we now find ourselves facing a decision based on the following three choices: combi, combi-storage or seperate boiler and storage tank.

I have a pretty good idea of the differences as told me by plumbers, so I was wondering if anyone out there had a more independent view based on personal experience.

Ours is a three story victorian semi. Two bathrooms and runs around 16 rads of which 9 are kept on (to varying degree's) and the rest turned on as and when needed.

Thanks

 

[Nemesis]

plethora of plumbers

Is that the collective noun?

I thought it was an extortion of plumbers - you learn something fresh daily.

:wink:

 

[Penners]

an extortion of plumbers

:lol: :lol: :lol:

 

[Horace]

I have recently changed my boiler and gone for a boiler with a separate pressurised hot water tank (mine is a megaflo but there are other types). Previously I had a normal hot water tank. In our house the pressurised cylinder (aka unvented cylinder) gives fantastic pressure for the hot water and works brilliantly. It recovers very quickly - 25 mins to completely heat another tank of water apparently)I don't like combis because the hot water performance is crap. In a previous house I installed a combi (Vaillant - good make apparently) and even with very good water pressure I thought the hot water supply was pathetic. I don't think they are that efficient either because I seemed to waste gallons of water waiting for the taps to hot up - not quite the instant not water they are supposed to provide! If there is more than one bathroom my view is that combi's are a waste of time. However plumbers like them because the pipework is easier. They also say things like "Oh combis are far better now etc" All I can say is I rented a holiday cottage in the Lake's with a brand new state of the art combi boiler recently and it was just as woeful as I remembered!

However, if your water pressure is poor a pressurised cylinder may not give you the performance you require (and a combi would be even worse). A traditional vented system with a tank in the loft may be the best way to go. The plumber should test the pressure and flow before recommending anything (that doesn't just mean turning on a tap!)

Hope that helps!

 

[Geoff Flegg]

Opinions vary, but here's mine.....

Like you, I too have a 3 storey Victorian semi - the boiler died 3 days after I bought the house! The boiler has to feed 14 radiators, plus hot water.

I was advised against a combi, as mentioned above hot water flows are poor. I put in a new condensing boiler and have a conventional un-pressurised hot water tank - it all works fine, if the hot water tank is emptied into the bath it takes less than half an hour to recover.

The opinions I got said that combi boilers are fine for smaller properties (esp. flats), but not so good on larger ones.

 

[chuckey]

My nephew had a four year old Vaillant oil combi removed because it was unreliable. Interesting to see an opposing point of view. My brother-in-law had an electric water storage system converted to a Potterton combi system, it lost pressure every 6 monthe for the four years he lived there. Probabley a small weep under the downstairs floor somewhere. What a pain!!
If you have the room for the water tank, I would go with electric water storage rather then oil, cos you can use solar to top it up and oil is only going to get dearer.
Frank

 

[Flyfisher]

After a plethora of plumbers visiting our house to quote (or not too bother quoting in some circumstances!)

I know the feeling only too well! I can understand that some tradesmen would take one look at a period property and decide they don't want that sort of work, but what's the point in coming out, spend a couple of hours discussing requirements, then phoning back with some questions but then just not bothering to reply! And when contacted after a couple of weeks they say "the quote's on my desk I'm just checking through it", but it never arrives. Is it really too difficult just to say 'sorry, but I don't do this sort of work'.
It would save an awful lot of wasted time all around!

But to the question at hand. We went through pretty much the exact thought process that Horace described and we also didn't believe the 'combi's are much better now' spiel. It's being installed at this very moment so I don't yet know how it will turn out.

The two other factors for making that decision was that a pressurised system eliminates a tank in the attic, which I thought would be an added bonus in terms of freezing risk and condensation risk. Probably not a big factor in the grand scheme of things, but I can't see a downside to not having a big tank of water in the attic.

 

[getcarter]

Its interesting to hear what you have to say. My own original preference was for a boiler and storage tank, as our top two bedrooms are in the loft space all I'm have as an actual loft is really only storage space....so a tank in the attic is out of the question, so a pressurized system seems to be the best way forward, I guess I'm wondering then does it justify the extra cost....you all seem to be saying yes on that one?

Yes I'd also want to say that plumbers are the most frustrating bunch for not quoting and I can't understand why they seem to be content both wasting mine and theri own time! As you say Flyfisher why not just say "sorry not my type of work".

Thanks for your comments....anymore gratefully appreciated

 

[Essex]

We had a combi with storage tank in our previous house, with 2 bathrooms, a cloakroom, a kitchen sink and a utility room sink, this was ok-ish until we had family/guests staying when only one of the above would get hot water. The boiler failed most winters, but always sorted by our service plan.
In our current house we went for an efficient condensing boiler and a vented hot water system (with solar cylinder piped for future solar hot water). I would never go back to the combi system.
Also just got LBC for our solar panel (on frame in garden by oil tank)

 

[Nemesis]

Also just got LBC for our solar panel (on frame in garden by oil tank)

Do please keep us updated with this!

 

[AMc]

Another vote for pressurised hot water tanks here- ours was fantastic and gave a great shower

We had a Megaflow with gas boiler in our 3 storey Victorian terrace (2 bathrooms) and the hot water pressure was great.
It did need 'regenerating' about once a year but that was no big deal - turn off the cold water, open a hot tap, open a vent then close when it stops dripping, turn on the water and turn off the tap when the water flows.

One thing to pay attention to is to get the overflow properly routed. Ours was just dumped onto the floor in the basement. So it took a while to work out where the puddle was coming from - the outlet drips when the tank is full, hot and needs regenerating. If the builder had fitted the tank on a plinth then the overflow could have gone into the butler sink next to it

 

[Flyfisher]

Another vote for pressurised hot water tanks here- ours was fantastic and gave a great shower

We were told the mains pressure is very important for a pressurised system because it will be the limiting factor in shower performance, among other things.

A low mains pressure means you won't get a decent shower (depending on your preferences of course) whereas with a non-pressurised system you can easily add a pump to increase the pressure. Apparently you can't do this with a pressurised system so you're stuck with the mains pressure - which may be fine for the heating system and baths but may be too low for a decent 'whoosh' in the shower.

 

[Geoff Flegg]

My own original preference was for a boiler and storage tank, as our top two bedrooms are in the loft space all I'm have as an actual loft is really only storage space....so a tank in the attic is out of the question

Depends on exactly how your house is constructed, but mine sounds very similar to yours. The conventional un-pressurised hot water storage tank is in the cupboard under the stairs that go from the first floor up to the attic rooms. The header tank is high up on the wall in one of the attic rooms, which is pretty ugly - however, there is a small loft space , the sloping attic ceilings don't go all the way to the apex of the roof. There's room for the header tank up there in that loft space (bearing in mind that they're not very big) - and that is where it will be moved to, one day when I get round to it!

We don't run a shower off our system - both our showers are electric - so I can't comment on the performance for that. There's plenty of hot water pressure at the sinks on the first floor though.

One limitation is that because the attic rooms are one floor above the hot water cylinder, the sink we have in one of the attic rooms has to have a small electric water heater. We only use it as a guest room so it's no great hardship, but I guess if you used it regularly it may be expensive to run.