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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Plumbing Questions >> converting from tank to mains pressure https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1285842397 Message started by highlandspring on Sep 30^th, 2010, 11:26am

Title: converting from tank to mains pressure
Post by highlandspring on Sep 30^th, 2010, 11:26am

Hi,
I manage a small block of very small studio flats (12) on basement ground and 3 upper floors. Mains pressure is good. All flats are have combi boilers.
It is believed at least 6 maybe more of the flats are already served from mains pressure.
The idea is to change all to mains pressure. My question is, this.
Some of the flats have old bathrooms(maybe 20 years old) My plumber says some ball cocks may require changing, but there is no chance of any major leaks at time of change over and the worst will be dripping overflows. Whilst he seems confident, I am just concerned that other taps in the flats may be affected, and is he correct in his confidence that the worst that will happen is a dripping overflow
The problem is trying to get access to all the flats at once is proving to be a logistical impossibility.
Any advice gratefully received.

Title: Re: converting from tank to mains pressure
Post by thescruff on Sep 30^th, 2010, 3:05pm

Theoretically he is correct.

Old heating system can leak, radiators and old pipework can leak, ballvalves currently on low pressure should be changed to high pressure, existing taps, showers etc will be low pressure so can drip/leak and need replacing, as may radiator valves.

Modern boilers may be difficult to locate according to the regs about flue positions etc.

And then you have the biggest problem of all, the cold mains.

You need to think very carefully, and get the mains tested properly at peak and off peak times for flow rate (Ltrs/min) and pressure.

As a very minimum you would need a 32mm supply and possibly 50mm.

As above Theoretically he is correct, but that depends greatly on the age of the existing, I would say some leaks were inevitable on an older system.

Damage limitation can be achieved, by pressure testing the existing pipework, during the change over.

Title: Re: converting from tank to mains pressure
Post by CWatters on Oct 1^st, 2010, 8:32am

What scruff said.

The mains pressure might be ok currently but will the flow rate and pressure still be ok when all 12 flats are taking a shower. Depends on the bore, length and layout of the pipes used to supply the block and the flats.

Title: Re: converting from tank to mains pressure
Post by thescruff on Oct 1^st, 2010, 1:37pm

What would normally happen, is you would have a service room, with say a 50mm supply, the 12 stopcocks and 22mm feeding each unit.

The gas would be the same, 12 meters, one for each unit, from a central area.

Personally I don't think it's the way to go, but that depends on the occupancy etc. are they let, lease or owner occupied.

District heating and hot water systems have many advantages, slashes your carbon footprint, can be used with renewable energy, solar etc, and invariably a lot less problematic to install in an occupied building.

You should look at the options, and take the best system within budget, not forgetting the access problems, unless you intend to chuck them all out for 3-4months.