Upgrading incoming main

[godisafrenchman]

Have been an avid reader of the forum for a while now, but this is my first post, so hello to all.

I am looking to update the heating and HW system in the new (to us, old to the world) house we have just moved into. At the moment we have a gravity system that provides next to no pressure to the 1st floor bathroom shower - which is less than 1m below the tank.

I've been advised by a few people to look into an unvented system as we would like to put a bedroom and en-suite into the loft space. I've read as much as I can find on these systems and realise that the incoming mains flow and pressure are vitally important. Therefore, to stop you all asking the same question - which I know you find annoying - the pressure and flow at present are:

Static pressure at washing machine inlet (just past kitchen tap) - 2.5 bar at 10pm and 2 bar at 7.30am
Flow from kitchen tap - approx 14l/min
Flow from outside tap - about the same, 14L/min
Dynamic pressure at washing machine when kitchen tap on full - 1 bar

As far as I can tell the incoming main is 22mm, I presume copper (?) but can't really tell - the house was built in 1953 if that helps. Pipework to kitchen tap (and washing machine) is 15mm copper.

I have had a couple of plumbers round, one of whom said we would be fine (without testing anything other than turning the kitchen tap on) and the other who measured the flow but not the pressure. Both are quoting for an unvented setup - although I was unimpressed with both of them so will be seeking more opinions.

I think that whilst the pressure is ok (not great but ok) the flow seems to be quite low. So my question is (finally) should I look into upgrading my incoming mains supply by fitting a new/larger pipe?
My real concern with this would be spending the x number of pounds it would cost without seeing any improvement. So I guess the real crux of the matter is - how do I know if upgrading the incoming main will give me enough flow and pressure to obtain good performance from an unvented system??

Sorry it's so long - I've got a load of info spinning round in my head and it's all splashed out at once.

 

[gas4you]

Firstly I do not think your current pressure and flow rate are good enough to warrant the expense of an unvented system.

This will need at least 3.5 bar and 20 l/m to be worthwile.

Increasing your incoming main size will increase the flow rate slightly but not the pressure, but whether it will increase by 50% is questionable.

Minimum size today is 25mm blue alcathene. The internal pipe work needs increasing to 22mm as well.

From your present figures you would me best with a mid power combi eg ecotec plus 831, as you don't even have the flow rate for an 837, 15.5 l/m.

Other options would be an accumalator, which I know nothing about, or upgrading the present gravity system.

 

[bengasman]

Kitchen and outside tap will be on 15mm, and probably the same pipe at that. Run the kitchen tap on full, and measure the flow from the bath tap at the same time. Chances are that a 22 mm mains water pipe will easily feed a 35 or 40 kW combi. As long as it does not dip under 2 bar, you should be okay. Static pressure in itself means little unless it is really low

 

[ctp]

look at whole house pumps it would mean changing dhwst but might save you money and you could do it easier than unvented/combihttp://www.techflow.co.uk/pdf/Turbo-install.pdf

 

[ctp]

ps.godisafrenchman ,eric canntonar

 

[gavinda]

depends how much you are willing to do yourself. i change my mains from the old black stuff to 27mm blue and ran 22mm copper up to my wb greenstar for mat cost only. the water board didnt even charge me for reconnection. as long as you plan well ahead its doable.

 

[joncox]

the water board didnt even charge me for reconnection. as long as you plan well ahead its doable.

Would like to hear more about how you convinced Thames Water (I presume) to waive reconnection charge.

I would like to upgrade my incoming lead main, but don't qualify for their free replacement. TW reconnection charges as listed are very expensive...

 

[gavinda]

just lucky i guess. . i spoke to them befoire startuing work and was advised it would cost in the region of £4-500 to reconnect . i asked what i would need to do and got on with it. dug the trench laid the pipe, fitted new stopcock and had all the internal pipework clipped earthed and ready to go. then called tvw back for inspection. the guy that came out was happy and said they'd be back in a matter of days. when i asked about the final price he said not to worry and that the quoted charge is used to discourage builders from breaking stopcocks to obtain a new one . i was not one to argue. 2 days later they arived, dug up the path connected my new mains and fitted a new stopcock.

jobs a goodun.