Is moving to mains pressure hot water possible with only 7 litres minute?

[nmg196]

We are considering a loft conversion which may require removal of the cold water tank. However I've read that water pressure should be at least 10 litres per minute for something like a Megaflo and having measured ours a few times, it's only about 6 or 7 litres a minute. Are there any solutions to removing the cold water tank on a house with low pressure? We could possibly fit a tank in if it was vertical (like a water butt) but what other options might be available?

 

[cross thread]

New water service.

 

[Madrab]

Nothing less than 15L/Min 2.5bar dynamic for an unvented and even then that's really the lowest to make it worthwhile. Not sure where you got 10L/min from.

Time to get the mains tested to see what's available to you in the street.

 

[nmg196]

Not sure where you got 10L/min from.

Actually I have no idea - I just searched again and it's more common to see 15 or even 20L/min.

 

[nmg196]

Perhaps I'm better off keeping the vented setup and finding somewhere to relocate the tank or fit a vertical tank instead.

 

[Johntheo5]

Maybe invest in a 0 to 10bar pressure gauge that can be attached to say a outside tap and monitor the static pressure then open a few upstairs taps to get a total of say 15 LPM and note the dynamic pressure.

 

[Madrab]

Perhaps I'm better off keeping the vented setup and finding somewhere to relocate the tank or fit a vertical tank instead.

Try and stay away from horizontal cylinders if you can, they aren't the best.

You say you have 6>7L/min, where is that measured from? Are you rural? If you call up your water transporter and ask them to check the mains as you're having supply problems and can they confirm what the mains is delivering. Be there on the day if you can and offer the chap tea 'n' biscuits and quiz him as to the flow and pressure figures. Their reading will always be dynamic as the mains is in constant use.

 

[nmg196]

You say you have 6>7L/min, where is that measured from? Are you rural?

It's measured from both the kitchen tap (near stopcock) and also at an outside tap. The flow seems identical at both locations. I'm not rural. I guess I should ask some neighbours if theirs is the same. However since posting the above I've found the utility room tap is closer to 10L a minute so perhaps the kitchen tap simply has a narrow bore or something.

 

[Johntheo5]

Can you measure the total flowrate with both open, ideally the pressure should be monitored as well wih a pressure gauge on the end of another (non flowing) tap.

 

[Madrab]

Yep, as suggested you are looking for a dynamic figure where more than one outlet is open at the same time, this provides a better understanding on what the supply pipe can deliver, again though give your transporter a call and ask for a mains check. This will give a proper starting point as to what the communication pipe is capable of and whether its your pipework causing the bottleneck.

 

[Bod ...]

Have you got room for a break tank and a booster pump?

 

[Johntheo5]

I have a run of 22M of (53 year old) hydrodare piping, 21mm OD X 11.5mm ID between the street stopcock and just after the house stopcock.
The last readings showed 3.4bar static (at the house) and 2.5bar (dynamic) with a (upstairs) shower flowrate of 8.4LPM and 3.6bar/0.95bar through a bath (mains) tap at a flowrate of 14.4LPM, one has to be careful because the bath tap has no back pressure at the outlet, if all my pipework was increased to 22mm, (19mmID) then would probably get ~ 2.2bar dynamic at the house and > 14LPM from the shower from a static pressure of 3.4bar.