I have got an old potterton bolier providing DHW/CH via a cylinder and
header tanks. The boiler is an old cast iron one and is absolutely
fine but at some stage it will need replacing. The obvious thing to do
is replace like for like and continue with the system I have got. The
other option is to replace with a combination boiler and remove the
old cylinder and tanks to create extra space in the bathroom and loft.
I'm prepared to give this a go myself if the sequence of events is
logical. What considerations are there in converting from the old
system to combi boiler? The pipework will obviously change but not to
drastically. The pump is upstairs in bathroom. This will need to be
removed as new pump will be in combi downstairs. The cylinder and
header tanks will need to be removed and relevent pipework
reconnected. Will taps, cistern washers etc need uprating?
And finally if I do go down the combi route, what size/type would be
recommended for a 3bed 3reception house currently let out as a 5 bed
1recepion with 1 kitchen and 1 bathroom (with electric shower, which I
could convert to thermostatic).
Any help gratefully received
The 'right' sort of plumbing for this calibre of home would be
a) Unvented mains cylinder + non-combi boiler. - if that is beyond the
budget which will likely need a
water main upgrade.
b) Vented mains cylinder + non-combi boiler.
Combi can and sometimes are fitted to this size of house but that would
be a personal choice rather than standard practice.
You don't have to have a combi to get many of the other benefits like
sealed primary etc.
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
What cistern washers? The WC cistern will currently be fed from the cold
rising main, only hot taps will be affected. If the cold taps are currently
OK the hot taps will probably be OK also (same age).
Ed if his 5 tenants are currently happy sharing a single electric shower why
make waves? (Sorry weedy pun!) They must be intrinsically very clean people.
It's not a 5 bedroom executive residence with 5 en-suites, it's a 3 bed
house turned into 5 bedsits, the boiler still has the same number of
simultaneous outlets to service. Anyway, bedsit denizens can only expect
It's questionable whether anything really needs to be done. I would
personally be happier with no tanks in the attic, especially in a house
rented out, would anyone know what to do if something went wrong in the
The existing cast iron boiler might run for 5 - 10 years more without
problems, and be cheaper to repair anyway, a combi might break down 2-3
times in that period.
What is this standard practice you are on about?
Unvented cylinder? A vented heat banks is far superior in many aspects.
many councils have been bitten by unvented cylinders and are going
overflowless heat bank.
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com ).
I did it recently. It was a doddle.
The mains water feed to central heating loft tank was connected to what used
to be ch feed pipe and was now connected at boiler end to cold water inlet
for hot water.
The combi hw outlet was teed into the hw pipework at a convienent point.
The ch feed and return were connected to new boiler same as old one.
The cold feeds that were fed from the large loft storage tank were fed from
The vent pipe, pump and hw cylnder and loft tanks were redundant.
After switch on the only problems were the odd seeping rad valve that didn't
like the new sealed system pressure,
cured by spannering and the Fernox stuff you can inject into a rad bleed
valve, the odd toilet washer valve that had to be changed from low pressure
to high pressure type.
The shower was changed to a Screwfix trad mixer type and this is very good
on the combi output.
Don't go for boiler which is less than 28kW, preferably more. This will be
perfectly ok for a 1 shower setup.
I used a Vokera boiler mainly because it was inexpensive and it has a rear
entry flue which looks neat.
Supplier was mrcentralheating.co.uk, you have to phone them up to get boiler
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