New boiler help

Hello,
I live in a three bed house with my partner. It's a three storey
property with a toilet on the ground floor and a bathroom on the first
floor and radiators throughout. We've inherited an old central heating
system which consists of a gas boiler, hot water cylinder and header
tanks etc.
Next year we're looking to rip out and redo the entire ground floor of
our house. As part of this project we plan to get rid of the existing
heating system (the boiler is on the ground floor), and replace it
with a combi boiler. I've read the combi boiler FAQ on this site and
am happy with the compromises this brings.
My main concern is that of pressure/flow. Currently our cold tap in
the kitchen doesn't have very strong flow. It's OK (a plumber did
measure the flow and thought it was OK), but not fast flowing. We want
ensure that we have a really good shower (on the first floor) and are
concerned that there's won't be anough mains pressure to supply this.
A builder recommended that we use a Megaflo to resolve this, but I'm
not actually sure we have a problem. I checked the mains pipe which
runs from the front of the house and it's 15mm. Could this be
restricting the flow?
How can I find out for sure if the mains pressure will be suffient for
a good shower?
Reply to
ben
Measure how many litres/min flow you get from the cold tap in the kitchen and report back. Next time ask the plumber for the number, not OK. If you have doubts about the mains pressure at ground floor level you also need to find out the ground floor static pressure to gauge what the static pressure will be at first floor shower head level.
The builder is talking nonsense, the Megaflow won't resolve the pressure problem, it's the other way round, a Megaflo needs a good pressure/flow. Vented against unvented has been done to death here so look up the threads.
Jim A
Reply to
Jim Alexander
Find you best performing tap and test the flow rate with a container of knows size and a stopwatch. If you are getting 15 lpm or less then any mains fed system will perform poorly without significant additional work. 15 - 20 lpm is marginal, and 20 lpm is usually fine.
It will yes.
Peoples expectations of "good shower" vary wildly.
Reply to
John Rumm
...that's not to say you can't possibly get a perfectly OK shower if you have a 15mm rising main, more that it's a potential contributory factor if you find you have an unacceptably slow flow rate.
David
Reply to
Lobster
Thanks for all your replies. I've just measured the flow rate from the kitchen tap: We get 5.7 litres/min.
I guess I now need to get a static pressure reading to see if the pipes are restricting the flow, or if there's just a lack of pressure in the mains. I did speak to Thames Water a few months ago and they said that there should be 1 bar of pressure in the mains...
Reply to
ben
On Mon, 19 Nov 2007 10:32:35 -0800 (PST) someone who may be this:-
Even if you consider that an acceptable shower, consider what will happen to the shower flow rate when someone operates an appliance elsewhere in the house.
It seems to me that a storage system would be better, with just the kitchen cold tap fed from the mains. If the bedrooms are all upstairs then the shower should be there. I would try a gravity fed shower, but lay it out with an eye to converting it to a pumped shower if that proved desirable.
Around here the static pressure in the mains is five times that.
If that is all they are offering then I doubt if increasing the supply pipe size will make much difference to the pressure, though it may make quite a difference to then flow rate.
Reply to
David Hansen
That FAQ is 20 years out of date. Combis do not compromise. Want a one that can do 3 bathrooms? There is one there.
Reply to
Doctor Drivel
They specify a minimum flow too. Usually 9 litres/min. It may be worth your while get a new 25mm main back to the stop cock. You will never regret it.
Reply to
Doctor Drivel
this:-
Best a cold water storage system that adds value. An accumulator. This will provide the volume required and pressure at the static pressure of the mains. The accumulator is a large round pressure vessel. Or two small ones.One of these and combi solves many problems in the house if the water mains cannot be uprated.
He should firstly get the mains pipe sorted out. Doing that may bring dividends, and that is all he would need.
Then he needs decent combi boiler with decent flowrate.
Reply to
Doctor Drivel
So you have got no basis for combi, thermal store or unvented DHW without sorting the mains. Ten years ago I paid over £600 for a new 20mm connection. On the other hand you have a three storey house, ideal for a storage system with reasonable head. A possible interim solution might be to retain or improve DHW storage, but have a combi feeding only the kitchen sink initially if you are determined to have a combi.
Jim A
Reply to
Jim Alexander
We are a bit limited on space in the upper floor of the house (we don't have a loft) which has a big influence on our decision for a combi.
Our next steps are to get a plumber in to give us a reading of the pressure, then get the 15mm pipe upgraded if the pressure looks OK.
Reply to
ben
On Mon, 19 Nov 2007 12:22:14 -0800 (PST) someone who may be this:-
A hot water cylinder, like any other source of hot water, should be situated near the tap used the most, which in a house is usually the kitchen tap. The second floor is unlikely to be the best place for a hot water cylinder.
Reply to
David Hansen
Indeed, did not intend to give the impression it was inadequate, only that it will have a bearing. I have a 15mm water main into the house and it can supply about 18 lpm, which while not ideal, is ok with our 35kW combi. One shower works very well, and it can just about manage two at once if you don't mind a drop in the force of the shower. Its not so good if the washing machine or dishwasher is filling while you shower though.
Reply to
John Rumm
That is pretty poor really. IIRC the water supplier has a duty to provide a reasonable flow rate of at least 9 lpm.
Have you tried at other taps, such as an outside tap if you have one? Some kitchen taps have very small water paths, that can give overly pessimistic flow test results.
1 bar is the minimum really. If your static pressure is that low, then even a storage system may have problems in a three story property if you need to place a storage cistern at the top (1 bar is equal to 30' of head).
One quick test to try is can you block off the flow of the cold main by sticking your hand over a tap. You would not be able to do that if the pressure is much over 1 bar.
Reply to
John Rumm
> We are a bit limited on space in the upper floor of the house (we > don't have a loft) which has a big influence on our decision for a > combi. > > Our next steps are to get a plumber in to give us a reading of the > pressure, then get the 15mm pipe upgraded if the pressure looks OK. Good approach.
Reply to
Doctor Drivel
It is if the pipes are run separately from the cylinder and the cold water feed from roof tank to cylinder is adequately sized.
Reply to
Andy Hall

Site Timeline Threads

  • Soooooo since no one is mentioning building something I'll mention the POS I...
  • site's last updated in

    Woodworking

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.