Aqualisa showers and Expansion tank

ThisIsWeird

diz79 said:

Im now thinking to change the cylinder to unvented as its quite old now,

Ive been loooking at water pressure and it isnt really great this is what I have
Water pressure
10 secs 60secs
Kitchen 1.3ltrs x6 7.8ltrs
Outside tap 1.5ltrs x6 9ltrs
Bathroom 2.1ltrs x6 12.6ltrs
15ltrs p/ minute good water pressure
10-15ltrrs p/m acceptable
Anything below is poor
I think the reason the water pressure is highest in the bathroom is because thats where it comes in, its an old house.
Is the pressure good enough for the bathroom do you think? Also it seems the property has always had vented, so how do I know if I can go with unvented and does unvented help with the water pressure at all?

From what you say, the maximum incoming cold mains flow is 12.6lpm. Unvented cylinders are 'powered' by this cold mains, so that means the most you can have, Hot and Cold, with an unvented system is 12.6lpm. Ie, certainly no better than what you currently have.

Yes, it would mean that the H&C would now be balanced, but it would still not be a good flow rate.

Solutions? The most tried and tested is to install a large CWS in your loft, supplying a new DHWCylinder in that cupboard. The CWS could also supply the cold for the shower, so both HandC would now be balanced, albeit at a gravity pressure, and not mains; you'd need to choose a shower mixer that's happy with gravity.

Or, you do fit an unvented cylinder, but also a means of boosting your mains flow. If the cause of the poor supply is the incoming mains pipe, you could replace that. (You'd check with neighbours what their flow rates are). Or, you also install a pumped accumulator - but that's more space taken up, and a further £1-2k.

FreeBear

diz79 said:

Im now thinking to change the cylinder to unvented as its quite old now, 

Ive been loooking at water pressure and it isnt really great this is what I have


Water pressure
10 secs 60secs
Kitchen 1.3ltrs x6 7.8ltrs

Outside tap 1.5ltrs x6 9ltrs

Bathroom 2.1ltrs x6 12.6ltrs

15ltrs p/ minute good water pressur

Kitchen - Monobloc mixer tap ?

Those things are plumbed in with 6-8mm bore pipes which severely restrict water flow. With 12.l/min at the bath, you have excellent flow (better than my ~9l/min). Upgrade the cold water feed to the tank to 22mm, and go for an unvented system would work. Saves messing around with pumps.

A couple of other (more expensive) options - 1) replace the tank & heat only boiler with a combi, or 2) Install a heat pump complete with an unvented tank. With the current £7500 Boiler Upgrade grant, the cost may not be as high as you think. Octopus had given me a very, very competitive quote earlier in the year of £2700 (subject to survey) - That included heat pump, new radiators, and an unvented DHW tank.

diz79

Hi sorry for late response, thanks all for the input, ive been looking around and also spoke to a plumber fried and I think Uvented may be the way to go, do you have any recomendations, these are the two ive looked at, what do you think of these?

https://www.plumbnation.co.uk/gledhill-direct-stainless-200l-unvented-cylinder-303-4989

https://www.mrcentralheating.co.uk/everflo-indirect-210l-unvented-cylinder-and-kit

bjorn_toby_wilde

I’d get a reliable plumber and go with the brand they recommend and regularly fit. Good plumbers don’t fit brands that go on to cause them
lots of problems.

Ours is Heatrae Sadia but I think they’re at the top end of the price range.

One thing to note is that when Freebear says to upgrade the feed to the unvented cylinder to 22mm that means change the entire length of that pipe from the main to 22mm. Can you access it all? Lots of floorboards to take up and maybe it will run behind kitchen cupboards too. If you can’t then that will affect performance because the flow may not be adequate. Your plumber will know.

When we first moved to unvented our feed was 15mm and so was the incoming main. It was better than tank fed but not much. The real improvement came when we went to 22mm and installed a new main as we extended the house.