Complete install with low mains supply pressure

[Charnock]

Hello All,

I've trawled through a lot of the posts on here but I can't seem to find a solution for my situation. I'm GS Reg'd and my main experience is combi fitting in small to mid size houses, one bathroom or two baths, one with electric shower so no problem with DHW demands.

Now though, a friend has bought a big house which is currently 4 bedrooms and 2 bathrooms with a likely 5th bedroom in the attic in due course. He needs the entire plumbing and heating sorting from scratch but his mains water supply pressure is poor. The standing pressure is 1.1 bar and this drops to 0.25 working pressure with one tap open and giving a flow rate of about 9 litres a minute. Having spoken to the neighbours it seems that this is the same for all the houses in the area so even though he's going to upgrade the existing lead supply pipe we're not expecting much improvement. The current setup in the property is large header tank supplying both the hot and cold water requirements.

Would I be right in thinking that the only option is a vented cylinder? I'm thinking of installing the 30kW Vitodens 200W to make sure I cover his 18kW heat requirement with plenty for the tank but I want to make sure that if the pressure is improved at any point in the life of the system he can make the most of it without having to change too much of it.

I am assuming that I will have to keep the header tank for the hot and cold supplies to maintain good flow for the water supply but I'm not sure if other options would be better. Particularly, would a large accumulator give better flow rates? I wondered about a 500L accumulator with a pressure reducing valve set perhaps at 0.75 bar on the outlet to try to sustain the water pressure in a sealed system to provide prolonged hot water supply at a greater pressure but I wondered if the benefits don't really meet the cost of installation.

Hope you might be able to help me out,
Thanks.
Charnock.

 

[anz]

You say the house is connected via a lead main.

Do you know if this is via common supply pipe.

If it is, then after upgrading the supply pipe and connecting directly to the mains you may see a considerable rise in pressure.

 

[aqualogic7]

if you upgrade supply pipe pressure will still only be 1.1 bar but flow rate might be improved

 

[aqualogic7]

you could pressurize house by fitting a pump on out let from existing cwsc and use cwsc as a brake tank

 

[Roger Welton]

I suppose the ideal solution would be a booster set to increase the water pressure to the house and an unvented cylinder, cost may be prohibitive though.

 

[Charnock]

Thanks for all the responses. The incoming mains supply is solely for this property as far as I can tell... there seemed to be one external stop tap for each property.

RW - what do you mean by a booster?

 

[Roger Welton]

Thanks for all the responses. The incoming mains supply is solely for this property as far as I can tell... there seemed to be one external stop tap for each property.

RW - what do you mean by a booster?

Basically storage tank fills with water from mains, then pump provides increased water pressure and flow to all pipework in the property.

The Grundfos Home Booster | Grundfos

Booster Sets

 

[Charnock]

The Grundfos Booster looks like a great piece of kit but is a touch pricey. If I put a 100 gallon cwsc in the attic and connect to the hot water tank with 22mm and even run 22mm for the majority of the length of the cold feed would I not get a decent performance for a much smaller outlay?

There are high ceilings in this place so the head will be much greater than most houses I've come across and I just want to ensure a good flow with hopefully the potential for two simultaneous showers from the one hot water tank. I'd also run 22mm supply pipe to the tank to get a greater flow to it.

 

[stevetheplumber]

it realy depends on what they want if there looking for high power showers and body jets etc youve got a lot of work to do however if they just want good baths and normal preasure showers then keep it simple use a gravity sytem with tanks depending on loft space you might be able to jack them up higher there are shower mixers out ther that work on low preasures an aqualisa with 6 foot of head gives a good shower
if you need more then use a decent pump with dedicated supplies for the showers only
the constant drive towards high preasure sytems isnt always the best route they can be noisy especialy ballvalves in wcs , prone to leakage especially at taps and showers and exspensive to maintain due to the preasure