Maximum Allowable Velocity
The worlds Major Plumbing codes limit the velocity in pipework to 2.4 m/s, and sometimes even less for hot water pipes.
At present in Australia it is 3 m/s; but this will soon change to 2.4 m/s
There are three reasons for setting the maximum allowable velocity.

• To reduce piping noise
• To reduce ware and tare on fittings
• To reduce water hammer.

The free version of the program uses 2.4m/s. The Proversion allows the user to enter any value. However increasing the velocity above 3m/s should really only be done on underground pipes of straight runs with no bends or fittings, especially valves. But this will be outside the plumbing code. It may be justified in irrigation, fire flows, etc, or even in an area of high pressure when the dwelling is a long way from the source. But still not allowed under the plumbing Codes.
Lowering the velocity on the otherhand, would be advantageous.
Lowering the allowable velocity increases the pipe size, increasing the allowable velocity reduces the pipe size.

Minimum Residual Head
This is the pressure that we want to end up with at the last fixture (the worst case).
The Australian Code stipulates 5m. But this is likely to increase in the future.
Manufacturers recommend a minimum of 11m for most mixing and tempering valves. The Uniform Plumbing Code used in the United States also uses approximately this figure.
The free version of the program uses 15m as the residual head.
The pro version allows the user to enter any value.
Water will always flow from a point of higher head (pressure) to a point of lower head (pressure) even if the difference is only mm's. It may not flow very fast under these conditions, (a flat hydraulic grade) but it will flow.
So, if we have a house tank flowing under gravity to a kitchen sink (or similar fixture) with a standard tap (faucet), then we could (or may have to) lower the residual pressure to get water without having to rely on a pump. Provided we don't care how fast it comes out.

Pro Version
The proversion also has a table that displays the capability of every pipe size, for the claculated Hydraulic Grade, for both Copper and Plastic (Polyethylene).
That is :-

• How many dwellings each size can service
• What flow (L/s) each diameter can supply
• And what is the velocity in each pipe diameter.

The advantage of this, is that it is not necessary to keep changing the number of dwellings to find the pie size. because it is obvious from the table.
For example, it might show that a 25 dia can service 3 dwellings, and the next size up (32dia) can service 8 dwellings. So no need to calculate the pipe size for all the dwellings from 3 to 8, as the answer will be 32mm dia.
Also, showing the flow capacity of each size will help in cases where the flow is known. For example, irrigation, some fire services, and some mechanical systems.
If the velocity shown is the maximum allowable, then we know that velocity is controlling the pipe size, not the pressure.
Which means that we have plenty of pressure, which means that we should end up with more pressure at the end point than our desired minimum.

The Proversion also allows input of the number of individual fixtures. This is handy for large houses, or projects that have sheds, or something else as well as houses, or projects that don't have dwellings at all, eg industrial buildings, office buildings, shopping centers etc.

Proversion allows the user to change the maximum allowable velocity. This is useful for some other plumbing codes, or for hot water, or for some 5 star hotels that specify different velocities for different locations in the building.
Also allows the user to change the minimum residual head. Handy for tanks (lower residual head), fire hose reels or hydrants (higher residual head), or other fixtures where the manufacturer requires a different minimum head for proper operation eg mixing valves.

Pro version also calculates Pump Duty. If the hydraulic grade is so flat that a 32mm dia pipe is required for one dwelling (along with most of the internal pipework) then a pump size is calculated. This is also useful when pumping from tanks etc where the start pressure is zero, or it could be less than zero if the pump is above the tank.
When the pump duty is calculated, use the pump kPa pressure, (shown at the end of the page) as the 'Start pressure' to calculate the pipe sizes.

Screen Shots