Unvented cylinders and low flow rate

[pineapple]

My cottage has no cold water tank and the only hot water is from kettles or the electric shower! I've been quoted around £4000 for the installation of a 90 litre unvented cylinder to go in the under stairs cupboard midway between the kitchen and (ground floor) bathroom. Including pipework/connection to kitchen sink and bathroom and electrics.
It would enable me to take proper advantage of my E7. At present I run round like an idiot filing 5 litre flasks of hot water while on cheap rate and I try to fit in showers during that period too.
The quote seems very high and I'm in the process of getting more but does anyone know if a low flow rate affects the feasibility/safety of unvented cylinders? I'm still waiting for a proper answer from the company that provided the quote.
I have old pipework and am on a shared water supply with the adjacent property - hence the low flow.
Pressure is 3 bar but the flow rate in the bathroom is 10Lpm and just 4Lpm in the kitchen!
Edit:Not sure it is relevant but though circa 1750 the property is not listed or in a conservation area.
Cheers

 

[MikeG]

I've only got a second, but the answer might be an accumulator. Have a quick duckduckgo for that term......

 

[plasticpigeon]

Wouldn't want anyone to know you were looking for accumulators would you!

 

[MikeG]

If I follow the logic/ reference (Duckduckgo's USP as being the search engine that doesn't collect data on users) then no, that misses the point. I don't like the fact that Google can't be bothered paying their taxes. DDG also don't take bribes to push certain websites higher up the results list.

 

[Owain]

A low flow rate doesn't affect the safety, but it does affect the usefulness.

If you're on E7 I'd suggest at least 150 litres and more if you want to store cheap hot water for a bath. The new cylinders are very well insulated with minimal thermal losses so any unused hot water will be kept towards the next night.

 

[Me!]

The huge difference between 10 lpm in one room and 4 lpm in another suggests that you have a very restricted or partially blocked pipe somewhere between the two, or perhaps just the second tap doesn't open fully.
Personally, before investing that sort of money, I'd want to test the flow rate at the point the supply actually enters the property (or the point at which it will be connected to the new plumbing) so I could decide if that was sufficient when plumbed directly from there to the new hot water system. If it is not sufficient then I'd look at having a large cold water tank in the loft and a traditional vented old-style hot water cylinder.

 

[pineapple]

Thanks
The closest point to the mains is actually the bathroom (ground floor) where the higher flow rate is. That would also be the shortest pipe run to the cylinder.
There are stop taps both in the bathroom and the kitchen. I'm assuming the water supply first stops off at the bathroom then runs externally round the house to the kitchen (pretty thick cottage walls and flagged stone floor throughout). Have no idea how I would confirm that though other than dig around. Where's a water diviner when you need one? :roll:
I think I might discuss the flow rate issue with the actual cylinder manufacturers as I have yet to get a response from the would be installers.
Re size needed, the property doesn't have a bath.
So yes the discrepancy could simply be due to the state of the old pipework between the bathroom and the kitchen or maybe the kitchen stop tap - which I've got as open as possible. Had the water tested last year as I thought the pipes were lead. They aren't. Can't remember the material but the water company says they are the sort that get gunged up over time.
I could of course solve the flow issue completely by having my own connection from the mains and new modern pipework. I've always assumed that would be very expensive but maybe not.
I should cost the cold water tank option as well I suppose. But I've heard that when starting from scratch they tend not fit those much any more?

 

[Bogart]

3 bar is a good figure but the flow rates look a bit low.
And has been pointed out 90l tank is not that big especially as you use twin rate electricity.
I would suggest you register on

ukplumbersforums.co.uk

There are lots of very knowledgeable plumbers on there only too will to offer advice.