Expensive upgrade of incoming mains-worth it?

[indus]

Ok, so you want to exchange your thermal store for an unvented cylinder.
How do you expect to get 30lpm+ from it?
How big do you think the cylinder will need to be to service the 30lpm+ showerhead?
What head of water do you have?
Are you thinking of fitting a pump?
Why do you feel the need for a 30lpm+ showerhead?

Thank you

Firstly I'm not definitely saying I'll get a 30l/min shower. That comment was in response to Tony saying I could get shower heads even less than 15l/min.

What I would really like to do is run two 15l/min showers at the same time very easily, and perhaps even run a sink etc without any drop off in performance


[/b]How do you expect to get 30lpm+ from it?[/b]

I'm not sure what you mean. The cylinder will be supplying hot water only at a usual 60:40 ratio so will need to to supply 0.6x30 =18l/min.

Apologies if I have misunderstood



How big do you think the cylinder will need to be to service the 30lpm+ showerhead?

If I understand correctly you mean the volume of water I'd need to provide the hot water. A 300litre cylinder will run a 30l/min output (ie 18l/min hot water) for 300/18 = 16 minutes. This sounds reasonable though I'm even happy to have two unvented cylinders if needed.



What head of water do you have?

[/b]


Do you mean the pressure of my mains? It is at least 6 bar.

In terms of having a pump, well that's exactly the point. I'm trying to figure out if I spend the £4k will the flow increase enough such that I don't need break tanks, accumulators to store cold water and pumps to push the water around.


And finally I do take on board you comments about preserving resources, I do my bit in many other ways


Thanks for your help

 

[indus]

Ok, so you want to exchange your thermal store for an unvented cylinder.
How do you expect to get 30lpm+ from it?
How big do you think the cylinder will need to be to service the 30lpm+ showerhead?
What head of water do you have?
Are you thinking of fitting a pump?
Why do you feel the need for a 30lpm+ showerhead?

Thank you

Firstly I'm not definitely saying I'll get a 30l/min shower. That comment was in response to Tony saying I could get shower heads even less than 15l/min.

What I would really like to do is run two 15l/min showers at the same time very easily, and perhaps even run a sink etc without any drop off in performance



Question 1
[/b]How do you expect to get 30lpm+ from it?[/b]

I'm not sure what you mean. The cylinder will be supplying hot water only at a usual 60:40 ratio so will need to to supply 0.6x30 =18l/min.

Apologies if I have misunderstood


Question2
How big do you think the cylinder will need to be to service the 30lpm+ showerhead?

If I understand correctly you mean the volume of water I'd need to provide the hot water. A 300litre cylinder will run a 30l/min output (ie 18l/min hot water) for 300/18 = 16 minutes. This sounds reasonable though I'm even happy to have two unvented cylinders if needed.


Question3
What head of water do you have?

[/b]


Do you mean the pressure of my mains? It is at least 6 bar.

In terms of having a pump, well that's exactly the point. I'm trying to figure out if I spend the £4k will the flow increase enough such that I don't need break tanks, accumulators to store cold water and pumps to push the water around.


And finally I do take on board you comments about preserving resources, I do my bit in many other ways


Thanks for your help


Sorry can't figure out how to bold your questions!

 

[Charnwood]

Firstly I'm not definitely saying I'll get a 30l/min shower. That comment was in response to Tony saying I could get shower heads even less than 15l/min.
That's what prompted me to think 'what a numpty'

What I would really like to do is run two 15l/min showers at the same time very easily, and perhaps even run a sink etc without any drop off in performance
Is it likely that both showers will be run at the same time? whats wrong with sharing?

How do you expect to get 30lpm+ from it?

I'm not sure what you mean. The cylinder will be supplying hot water only at a usual 60:40 ratio so will need to to supply 0.6x30 =18l/min.
The showerheads(s) may be up to delivering 30lpm, but is the pipework up to supplying it? Your 60/40 ratio is based on ideal conditions, i.e. cylinder at full temperature. What if 2 people take showers consecutively. Person 2 will be getting "sloppy seconds" - cooler water in the cylinder. Unless you have a quick recovery cylinder.

How big do you think the cylinder will need to be to service the 30lpm+ showerhead?

If I understand correctly you mean the volume of water I'd need to provide the hot water. A 300litre cylinder will run a 30l/min output (ie 18l/min hot water) for 300/18 = 16 minutes. This sounds reasonable though I'm even happy to have two unvented cylinders if needed.
Bear in mind that all the time you are taking hot water from the cylinder it will be filling with cold for, feasibly, 16 minutes , slowly reducing the tempreature of the available water thereby altering the 60/40 mix.

What head of water do you have?

Do you mean the pressure of my mains? It is at least 6 bar.
EDIT: Ignore this answer - total codswallop!
No, I mean head of water from the header tank feeding the unvented cylinder. It will have to be fed from a tank. Unvented means sealed, i.e: between mains and tap the water stays at mains pressure. Vented means open, as in not directly from the mains but from a tank.

In terms of having a pump, well that's exactly the point. I'm trying to figure out if I spend the £4k will the flow increase enough such that I don't need break tanks, accumulators to store cold water and pumps to push the water around.
You will almost certainly need a pump if you go unvented.

And finally I do take on board you comments about preserving resources, I do my bit in many other ways
Good lad.

 

[neiltheplumber]

Most mixer showers I fit come with a 7l per min flow restricter or aerator and this gives a perfect shower! Same with taps.

You may have issues with internal pipe work if 6bar and 19l per min won't let you flush a toilet and shower at the same time?!

 

[indus]

Thank you

1) Yes, two showers will run together very regularly. If my wife leaves me and takes the children and an eighteen year old Russian move in, then I'll consider sharing

2) All the pipework to and from the cylinder will be upgraded and can be as large as needed to maximise flow rate. And yes I will have a quick recovery cylinder.

3) I am also prepared to install two unvented cylinders if needed.

4) Your post about header tanks has completely thrown me. I thought unvented cylinders/systems did NOT have a header tank. So I can't see why I would need a header tank with my unvented cylinders.

5) On what basis do you say I would definitely need a pump?

Thanks

 

[indus]

Most mixer showers I fit come with a 7l per min flow restricter or aerator and this gives a perfect shower! Same with taps.

You may have issues with internal pipe work if 6bar and 19l per min won't let you flush a toilet and shower at the same time?!

Thanks Neil.

The system does not actually run at 6bar, it has a prv set to 3 bar.

My current en suite shower is a Daryl modern hydra over head drench and looking on the web the flow rate at 3 bar is 19l/min. That increases further if the hand held unit is used as well.

With these figures you can see that as I am using a thermal store (ie mains instant heating) if I use the shower and then turn on any other outlet my shower takes a dive.

 

[Charnwood]

4) Your post about header tanks has completely thrown me. I thought unvented cylinders/systems did NOT have a header tank. So I can't see why I would need a header tank with my unvented cylinders.

It's thrown me too.
For once I was talking b0llocks.

5) On what basis do you say I would definitely need a pump?

On the basis that I was talking carp.

 

[indus]

4) Your post about header tanks has completely thrown me. I thought unvented cylinders/systems did NOT have a header tank. So I can't see why I would need a header tank with my unvented cylinders.

It's thrown me too.
For once I was talking b0llocks.

Perhaps if you didn't fret so much about flushing the toilet or brushing your teeth then your mind would be clearer

 

[The Baker]

I might be an idea to check how much water is currently available at the "outlet" of the Pressure Reducing Valve. (Assuming this has not already been done)

If the flow rate figure at the outlet of the PRV meets your needs then this points to the internal pipe work being undersized. (Individual isolators may be restrictive)

A previous poster asked about the head of water, I think they were enquiring as to the height of the building because given sufficient height and correctly sized internal pipe work, a couple of cold water storage tanks high up in the loft could give provide enough of water for the showers, leaving mains pressure for the other draw off points.

It is possible to lay out the pipe work so that 6bars gets all the way to some bits of the house and 3bar to others.(Cold Water Tanks at 6bar for quick top up)

I appreciate that altering the internal pipe work may not be something you want to do, however some PRV’s strategically installed around the house could be a useful addition to your internal plumbing.



Tim

 

[Charnwood]

It is possible to lay out the pipe work so that 6bars gets all the way to some bits of the house and 3bar to others.(Cold Water Tanks at 6bar for quick top up)

Sorry, but isn't that governed by flow rate, not pressure?

 

[Weedrip]

As a rough guide the flow you seek at six bar on a 32mm mdpe main which is only a a bit under 26mm bore will theoretically produce a flow of 28/29l per min at a velocity of more than twice the recommended velocity of flow through copper pipes, it move so fast it begins to cause erosion of the wall and unacceptable noise via turbulence. That would be under full flow conditions.

The best suggestion so far really is to maintain as high a pressure as is available and drop were needed for terminal fitments and any unvented cylinders making sure that you balance the pressures of any shower and mixer taps as appropriate.

You would however have quite large pipes supplying the mains within the house, ie 35mm copper, could prove costly and probably not a DIY job, but that of course would for you decide.
Would they [water undertakers ] also up the standing charges for supply of that size. That may also be a long term cost consideration.

 

[The Baker]

It is possible to lay out the pipe work so that 6bars gets all the way to some bits of the house and 3bar to others.(Cold Water Tanks at 6bar for quick top up)

Sorry, but isn't that governed by flow rate, not pressure?

I was working from the "a bit of both" recipe, as in every little bit helps, and as Weedrip points out the speed of the liquid through copper would spoil things, hence the CWS tank suggestion.

I am sure you would agree that its difficult to advise without actually visiting the house.

Tim

 

[Charnwood]

[water undertakers ]

 

[indus]

I might be an idea to check how much water is currently available at the "outlet" of the Pressure Reducing Valve. (Assuming this has not already been done)

If the flow rate figure at the outlet of the PRV meets your needs then this points to the internal pipe work being undersized. (Individual isolators may be restrictive)

A previous poster asked about the head of water, I think they were enquiring as to the height of the building because given sufficient height and correctly sized internal pipe work, a couple of cold water storage tanks high up in the loft could give provide enough of water for the showers, leaving mains pressure for the other draw off points.

It is possible to lay out the pipe work so that 6bars gets all the way to some bits of the house and 3bar to others.(Cold Water Tanks at 6bar for quick top up)

I appreciate that altering the internal pipe work may not be something you want to do, however some PRV’s strategically installed around the house could be a useful addition to your internal plumbing.



Tim

Thanks for your reply Tim.

Isn't the flow I've measured from the garden tap effectively the flow from the outlet of the prv?
The house is three storey and I would be happy to change the internal pipework if needed.

 

[indus]

As a rough guide the flow you seek at six bar on a 32mm mdpe main which is only a a bit under 26mm bore will theoretically produce a flow of 28/29l per min at a velocity of more than twice the recommended velocity of flow through copper pipes, it move so fast it begins to cause erosion of the wall and unacceptable noise via turbulence. That would be under full flow conditions.

The best suggestion so far really is to maintain as high a pressure as is available and drop were needed for terminal fitments and any unvented cylinders making sure that you balance the pressures of any shower and mixer taps as appropriate.

You would however have quite large pipes supplying the mains within the house, ie 35mm copper, could prove costly and probably not a DIY job, but that of course would for you decide.
Would they [water undertakers ] also up the standing charges for supply of that size. That may also be a long term cost consideration.

Thanks for your reply. I wasn't after the flow through the 32mm at 6bar as I assume a prv would always be needed and so was after the flow through 32mm at 3bar.

Also, if I turn the prv up to 6bar (when experimenting) the flow at my garden tap is close to 28l/min. So if that is the flow through my 22mm pipe at 6bar surely with a 32mm pipe at 6bar the flow should be alot more than the 28-29l/min you mentioned?

Thanks again