Flow rates with this combination of pipes/equipment

[CHRISX]

When you increase the pipe size on hot supply, it also increases the volume of system. Which means you will need to pull more cold water off before hot water occurs at tap/shower.(high water bills)
If you do not increase the pipe size on the hot you won't achieve much. So your between rock and hard place. From the new cylinder installation run a 22 mm up through the building and tee off at each floor, whilst doing that run a 15 mm secondary return from the highest point leg and back to cylinder ( if there are no long horizontal runs it may well work on gravity, saving the bronze pump costs)
It is also worth remembering that when comparing sizes of pipe, it done on Sq area.
Eg. 15 mm pipe 176 mm Sq
22 mm pipe 380 mm Sq
28 mm pipe 615 mm Sq
32 mm pipe 804 mm Sq
You can see a 22 mm pipe is more than double to that of a 15 mm pipe etc etc etc.
You will always be limited when working of mains supply as you have no control over available supply.
When the use of CWSC (cold water storage cisterns) were employed. One had a constant to work with, albeit low pressure the pipes could be sized according to the flow rates required. As the storage in houses reduces over time ( the installation of direct main systems, combi, unvented etc) draw lots of water from main system, which were not designed to provide such a demand. That is why you can expect lower provision during high demand times.

Hello justlead1,

I am trying to find out if / where I am going wrong regarding calculating the cross sectional area of the Copper pipe sizes that we have both mentioned in our posts:

I am not trying to be pedantic - just the opposite - I noticed that the figures in your message did not seem anywhere near figures that I have often Calculated / used when calculating pipework volumes so I did the Calculations again.

I also realise that the difference in these Calculations don`t really have much significance for this thread - but just to try and find out why they differ so much ?

My figures don`t come anywhere near yours.

I know that these internal diameters below are not exact - but rather than use something like `0.9mm wall thickness` / `13.2mm internal diameter` [15mm Copper tube] for example I have rounded up the wall thicknesses to 1mm - 1.25mm and 1.5mm -but they are not incorrect enough to have caused the difference in our figures - just for ease of calculations I have worked out my figures based on these internal diameters:

15mm pipe = 13mm internal diameter

22mm pipe = 19mm internal diameter

28mm pipe = 25.5mm internal diameter

35mm pipe = 32mm internal diameter

My Calculations then give:

15mm pipe - 6.5 x 6.5 = 42.5 x 3.142 = 132.74mm sq.

22mm pipe - 10 x 10 = 100 x 3.142 = 314.2 mm sq

28mm pipe - 12.75 x 12.75 = 162.56 x 3.142 = 510.771 mm sq

I know that You used a notional 32mm pipe but just to complete my Calculations - a 35mm pipe - internal diameter 32mm:

35mm pipe - 32mm internal diameter

35mm pipe - 16 x 16 = 256 x 3.142 = 804.352 mm sq

As I have typed this message with the Calculations I can now see that your figures are for the radius of the external diameters.

E.G: 15mm pipe - 7.5 x 7.5 = 56.25 x 3.142 = 176.737 mm sq

However your comment about 22mm Copper pipe being over double the cross sectional area and volume of a 15mm Copper pipe is still valid and well made to the OP.

I have continued to post this only because it took me so long to type this message - because I type with only one finger.

I assure You that I have not posted it to be `nasty` or to contradict you for any kind of `one up man ship` or any similar motive.

I hope that You will take this message in the way that it is meant - it is meant in a Friendly manner.

Regards,

Chris

 

[CHRISX]

Hello MrGatch,

As Member Shaun has stated the `Standard` pipe size for a new Mains Water Supply from most Water Suppliers is 25mm.

I would recommend having a 32mm diameter Main installed - this should give about 28% extra Supply Volume over the 25mm diameter pipe.

We cannot tell You on this Forum how your Mains water supply`s to various outlets on various Floors will or will not be affected by other outlets being opened - however I would definitely get the 32mm Mains pipe installed - it gives You a better chance of being able to use more than one or two Mains water outlets at the same time as some Hot Water outlets.

To try and ensure that there is very good Volume available at each Floor You would have to install a new `Rising Main` throughout the House - starting in 35mm pipe and gradually reducing as the pipe goes up - 35mm - 28mm - 22mm - that will add to the expense but just having an Incoming 32mm Mains pipe supplying the existing Rising Main pipe would not be advisable.

IF there is still a problem after having the 32mm Mains installed and upgrading the Rising Main pipework it would have been worse with a 25mm Incoming Mains pipe.

Regards,

Chris

Hello again MrGatch,

I apologise that there is an error in my previous message to You [quoted above] regarding the Calculation for comparing the cross sectional areas & volumes between a 25mm Incoming Mains Poly pipe and a 32mm Poly pipe.

I realised that I had made a mistake after I did some other Calculations in my last message above.

Actually a 32mm Poly pipe is about 78% larger in internal cross sectional area / volume than a 25mm Poly pipe.

Sorry for my previous error.

Regards,

Chris

 

[justlead1]

Good morning Chris
I applaud your questions regard plumbing system design. It gives me the opportunity to have an opinion and rant to an audience.
What is a fact surrounding your proposed system, is without changing pipe sizes. But removing combi and installing an unvented mains feed hot water cylinder will give better performance than the existing. Base on the fact that the frictional residence with combi units is high and water temp. is low.
However its nice to know when plumbing what performance will be achieved before carrying out the work, hence pipework sizing.
Head, pipe length, pipe size and discharge are the fundamentals. (Boxes formula) In the 60 is the arithmetic was time consuming using logs, anti logs etc. with calculators or spread sheet on Excel they are almost instant. An give a great overview of cost, performance etc.
My bitter and twisted attitude derives from those day when the code of good practise wanted 4 gallons per min at a domestic bath tap and 10 gallons per min if a public bath. Every time i see a combi i remember the hours of calc's spent pipe sizing. Coupled with the man hour wasted in the UK. People spending hours waiting for the bath to fill with warm water. Its what cheap buys.
On a brighter note, Once you have installed the cylinder and connected to existing, you can tweet it on a suck it and see approach. It may take up a few Saturdays but a good excise for proving theory and practise.
Good Luck with project.

 

[CHRISX]

Good morning Chris
I applaud your questions regard plumbing system design. It gives me the opportunity to have an opinion and rant to an audience.
What is a fact surrounding your proposed system, is without changing pipe sizes. But removing combi and installing an unvented mains feed hot water cylinder will give better performance than the existing. Base on the fact that the frictional residence with combi units is high and water temp. is low.
However its nice to know when plumbing what performance will be achieved before carrying out the work, hence pipework sizing.
Head, pipe length, pipe size and discharge are the fundamentals. (Boxes formula) In the 60 is the arithmetic was time consuming using logs, anti logs etc. with calculators or spread sheet on Excel they are almost instant. An give a great overview of cost, performance etc.
My bitter and twisted attitude derives from those day when the code of good practise wanted 4 gallons per min at a domestic bath tap and 10 gallons per min if a public bath. Every time i see a combi i remember the hours of calc's spent pipe sizing. Coupled with the man hour wasted in the UK. People spending hours waiting for the bath to fill with warm water. Its what cheap buys.
On a brighter note, Once you have installed the cylinder and connected to existing, you can tweet it on a suck it and see approach. It may take up a few Saturdays but a good excise for proving theory and practise.
Good Luck with project.

Hello again justlead1,

Are You mistaking me for the OP of this thread ?

I am not the person who is trying to achieve much better Mains Cold water and Unvented Hot water volumes at the outlets in his Home.

I previously gave an opinion on this thread about upgrading the Incoming Main pipe to 32mm Poly and also upgrading the Rising Main pipe starting at 35mm then reducing as the demand reduces to 28mm and then 22mm.

As You know in an `All Mains water` property the more Volume of Mains water that is available throughout the Home the better for both the Unvented Hot water Cylinder supply and the Mains water Cold supplies to various outlets.

But increasing the Mains pipework sizes as I described does not `Guarantee` that there will be a great Flow from the outlets - nor that more than 2 Hot water outlets can be used at the same time as that is limited by the 22mm Cold Feed to the Unvented Cylinder.

However - I feel that what I described gives the OP the best chance of being able to use Mains fed Hot and Cold water at more than one outlet at a time - although with regard to the unknown resistance of the existing pipework to various outlets what volume / flow will be available at the outlets is anyone`s guess.

I hope that You were not offended by my message to you of last night regarding the Pipe cross sectional areas.

By the time that I had almost finished typing my message including my Calculations I could see that your figures were based on external diameters - or possibly Copied & Pasted from a Table ? - because the message had taken me so long to type [I type with only one finger] I decided to submit it.

I was not trying to be pedantic or `trying to be funny` towards You.

Regards,

Chris

 

[justlead1]

Plumbings one thing reading another. Sorry Chris i seem to be lacking in the latter.