Boyles Law, P1 x V1
= P2 x V2, provides an inexpensive method to determine this volume.
Please see the diagram at the bottom of this page
At the outlet of the main reservoir add a full flow ball or butterfly valve
(Gate valves would work with consideration for multiple turns to open and close.
Tee in a 1” or larger line with shut off just downstream of the main
reservoir valve.
Connect this line to a 30 gallon (4 Cubic Foot) pressure rated tank or
reservoir.
Vacate any pressure in the 30 gallon tank and close dump valve.
The 30 gallon tank should have an accurate pressure gauge or transducer.
Close the outlet valve at the main reservoir.
Observe the pressure in the main line and rapidly (to prevent leaks from
changing the plumbing volume) open the valve from the main line tee into the 30
gallon tank.
Record the high pressure in the 30 gallon tank before it begins to decay.
P1 is the system pressure. V1 is the unknown plumbing volume. P2 is the test
tank pressure observed. V2 is the volume or the test tank plus V1.
For example use these numbers:
P1 = 100 psig P2 = the observed pressure, say 67 psig
V1 = ? unknown V2 = V1(?) + 4 Cubic Feet
P1 x V1 = P2 x (V1 + 4)
Then,
P1 / P2 = 100 / 67 = (V1 + 4) / V1 & 1.49
-1 = 4 /V1
V1 = 4 / .49 or V1 = 8.16 Cubic Feet of Volume
Record carefully and act rapidly to minimize the leak factor. If the volume in
the plumbing is great the pressure observed in the test tank will be high. If
the pressure observed in the test tank is very small the volume in the plumbing
is small.
Possibly for the first time you now know the volume of the plumbing in your work
area.
This will change a bit from time to time around the core value you have just
recorded.
In another White Paper, leak test calculation will add the plumbing volume to
the test.
