Expert: Paul Soderman - 10/24/2008

Question
QUESTION: How can i vary the length and width of a rubber or plastic tube /valve inserted  inside a garden house to create a garden hose that sequentially inflates from one end to the other  having 5 sections. For example, he second chamber won't inflate until the first chamber reaches a set pressure and then the third chamber won't inflate until the second chamber has achieved the same pressure as the first chamber and so on.  At the end each chamber will have equal pressures once completely inflated. Is there a formula for the length and width of the valve to be inserted to obtain this sequential inflation of 5 compartments with all compartments of equal pressure?"



ANSWER: Mark
Unless this is a trick question, I don't see why the same valve in each section won't do the job.  Say valve 1 opens at 5 psi, that lets flow into section two which charges valve 2, which opens at 5 psi, etc.  Volume of the sections only affect the time of inflation.  Did I misunderstand your problem ?
Paul

---------- FOLLOW-UP ----------

QUESTION: Paul
What kind of inexpensive simple valve can i buy that will open at a set psi and then close if the psi drops?
thank you

Answer
Mark
The most reliable and accurate valve for this application is a solenoid valve.  A solenoid valve requires electricity to operate and can be set to open or close based on a voltage sent by a sensor.  You would need a solenoid valve and pressure sensor to operate.  This is how my large water tank shuts off water from my well pump when a float switch sends a signal that the tank is full.  Pressure switches do a similar thing.

A check valve is simpler; it is spring loaded and opens when the pressure reaches the design level.  No power required.  They are not always accurate, but might function near the design spec.   Most check valves are designed for high pressure, but I found a drain valve at the following website that operates at 10 psi.

http://www.flomatic.com/index.asp?lg=1&r=275&pid=136

A good plumber or plumbing supply shop can give you more details.
Paul