Water flow for combi

gas4you

If you cant get 20 l/m+ and 3.5Bar+, then you are totally wasting your time and money fitting an unvented cylinder.

ListysDad

gas4you wrote: »

If you cant get 20 l/m+ and 3.5Bar+, then you are totally wasting your time and money fitting an unvented cylinder.

As mentioned I put in an UVC and accumulator into a property with 12l and 2bar and it worked just fine. Would agree that UVC or thermal store on their own would be a WOT tho.

OP To be honest this whole discussion is now well beyond DIY unless you fully understand what's being said and can measure the rates without having to ask.

IMHO its time to decide what you want as an end game and call in the pros to achieve it. Good luck.

drummer_666

I had the waterboard out yesterday, he couldn't get proper pressure reading as there is no OS tap.

He said from what he could get pressure was 2 bars, but couldn't measure if it was holding constant. Flow is approx 9l/min

It's cause there is one supply for about 40 houses and the only way to improve is to get a private single supply. Not an option to me due to costs

So do you think my best option is to keep to a conventional boiler and to get new cylinder and move it, either into loft if it will take it, or elsewhere if not (it is currently in what will be the entrance when the wall is knocked down and stud wall added)

How do I know if my loft will hold a tank AND cylinder?

Thanks

southcoastrgi

in layman's terms if you change to a combi the whole of your house both hot & cold will be supplied by a mains supply giving you 9 ltrs/min so i'll tell you what will happen, you turn on a tap downstairs & the water upstairs WILL stop, so no i wouldn't recommend you have a combi, the pressure in your taps shower etc in a conventional system ie cylinder & roof tanks is all about head of water this means the distance from the bottom of your roof tank to the outlet on the top of your cylinder so the further these are apart the greater your pressure (think of an old fashioned wc with a high level cistern what a great flush they used to give compaired with a modern close coupled one), so no i wouldn't recommend moving the cylinder to the loft you may not be able to get the roof tank high enough to make it work anyway & your pressure will be cr*p plus you will have all the hassle of frost protection.

drummer_666

keithgillyon wrote: »

the pressure in your taps shower etc in a conventional system ie cylinder & roof tanks is all about head of water this means the distance from the bottom of your roof tank to the outlet on the top of your cylinder

I thought it was about the distance from the cold water tank to the source of water i.e shower/tap, not distance from CWT to HWC?

cold water tank isn't in loft at the mo, it is about a metre above HWC in the bathroom

southcoastrgi

drummer_666 wrote: »

I thought it was about the distance from the cold water tank to the source of water i.e shower/tap, not distance from CWT to HWC?

cold water tank isn't in loft at the mo, it is about a metre above HWC in the bathroom

well it is to a certain extent but then we are getting into all the other info that is on your thread, i was trying to make it simple for you, the outlet of your hwc at the mo is about the height of your excisting taps give or take, if you put the cylinder in the loft then gravity plays a part but you still need to take into account the static head of water from your (& if we are using abbrivations then it's) cwc (not cwt) to the hwc, unless you have an extremely high loft then your static head will be min, yes by raising the "tank" this will help any cold outlets connected to it but by moving the cylinder you will be reducing the head of water to the cylinder & the only way to get more water in will be to increase the size of the pipe between the hwc & cwc this will increase the flow rate but not the pressure, flow & pressure are two totally diff things, ie turn down your incoming stop tap the flow out of your taps is reduced but the pressure is the same it just looks less.

drummer_666

so basically, it's prob a good idea to move the cwc to the loft and keep the hwc in the house

Also, at the moment I'm pretty sure I only have one water tank

Water man said downstairs is fed directly from the mains and upstairs from the cylinder...

southcoastrgi

nothing in houses is normal but yes 9 times out of 10 the downstairs is fed from the main (drinking water) & upstairs is fed from the tank in the roof (or in your case above the cylinder), sometimes the bathroom basin is fed from the mains too to give drinking water upstairs, "normally" if you only have one pipe coming out of the roof tank this will go to your hot water cylinder if there is two then the other prob goes to the bathroom. & yes i'd put the tank in the roof as high as you can get it (but still allowing for maintainence of the ballvalve) & keep the cylinder in the house.

drummer_666

There actually isn't a basin in the bathroom... very strange!

and for one more question today lol (thanks for answering)

how do I find out if the roof will hold the weight of the water tank ok?

southcoastrgi

it should be fine, you will need to build a stand to sit the tank on & this will need to spread the weight over serval ceiling joists, so just put the first timbers something like 8"x 2" will be ok & edge up not flat ACROSS the existing joists normally between 4 & 6 joists will be fine then build your stand off of those