Advice needed on moving to Combi or not please

[carl4x4]

Hi, We have a bit of a problem with the upstairs of our house which is necessitating us moving the current gravity fed hot water tank away from the airing cupboard. (long story short - 80's house, the water tank was too large and not suported sufficiently underfloor and has caused cracks, moving tank aleviates the problem)

The existing system is a Potterton boiler in the kitchen with cold tank in loft and gravity fed hot tank in 1st floor airing cupboard.

We have had three heating engineers round and have three slightly different views:

1) Keep existing 10 yr old boiler, replace with Megaflow type tank in loft, the loft is quite shallow so tank would probably need to be on it's side (a bit of web trawling looks like Telford make one)

2) replace cold tank in loft with coffin-tank raised on some sort of structure to get it high enough above a new horizontal traditional vented water tank

3) replace boiler and all tanks with Combi, install in loft so as to not destroy the fairly new kitchen

I like the idea of the Magaflow (plumber measured water pressure at outside tap as 3bar) yet to measure flow litres pm, but this still leaves me with a 10 yr od boiler which could cost me another small fortune in the future...

I have severe doubts as to the viability of the coffin-tank route in the loft and it will also add an additional 200kg or so weight up there!

We have been advised to consider a high capacity combi with some storage such as the Vaillant ecotech 937, my wife is sceptical on combi's as her experience is from a few years ago where you couldn't have two hot taps running without severe water pressure drop.
The house is a 3 bed detatched, radiator CH, two bathrooms, one with a power shower & bath (Power shower will go if we have the combi) and the other has a electric shower that heats it's own water direct from a mains feed.
I guess I'm after some advice as to what the best route is, the Valliant 937 sounds like a good idea to me as I get a new boiler and hot water but will it be sufficient for our house.

Thanks in advance

 

[Whitespirit66]

If you can get the coffin tank properly supported in the loft, then it sounds like the cheapest option.

Next on my list would be the unvented. If you have the pressure and flow, it would also be suitable for a 2 bathroom house. You can then bin all of the electric and power showers which will lower running costs a bit. Also, you can keep your existing boiler, which being heat-only may be good for another 5 or even 10 years.

 

[carl4x4]

thanks, we have a 15mm mains coming into the house, is this a problem for megaflow type systems?

 

[bengasman]

thanks, we have a 15mm mains coming into the house, is this a problem for megaflow type systems?

Yes.

Are you talking about a real PRESSURE drop, or is it a FLOW problem?

 

[carl4x4]

I don't know if we have a problem yet sorry, I just did a crude test and in a minute our outside tap (and utility room tap which hasn't got a restrictor in it) filled up 12.5 litres of water into a bucket. Is this a viable reading or not a good way to measure it?

 

[mickyg]

I don't know if we have a problem yet sorry, I just did a crude test and in a minute our outside tap (and utility room tap which hasn't got a restrictor in it) filled up 12.5 litres of water into a bucket. Is this a viable reading or not a good way to measure it?

its enough to tell you your water pressure/flow isn't up to much and both a combi and an unvented at this stage look like very bad ideas. I would stick with a vented tank system if i were you. Either that or you'll need to find a way to increase your cold supply, which means a pipe upgrade from the road.

 

[carl4x4]

I don't know if we have a problem yet sorry, I just did a crude test and in a minute our outside tap (and utility room tap which hasn't got a restrictor in it) filled up 12.5 litres of water into a bucket. Is this a viable reading or not a good way to measure it?

its enough to tell you your water pressure/flow isn't up to much and both a combi and an unvented at this stage look like very bad ideas. I would stick with a vented tank system if i were you. Either that or you'll need to find a way to increase your cold supply, which means a pipe upgrade from the road.

That's exactly what I was thinking, I'm now looking into relocating the current vented cylinder downstairs in the utility room, at least we know it'll work and there's enough room for me to knock up an airing cupboard !

 

[ajrobb]

A new cold water storage (CWS) tank would have to comply with new regulations (bye-laws) to prevent ingress of animals into potable water. My 1978 house had all cold taps upstairs fed from CWS in the loft.