One of the most important considerations when designing a system is to keep the inlet simple. You should try and stay away from angle fittings, bushings, restrictive filters, small diameter hoses and non-full port fittings and valves.
Three types of feed conditions:
1) Pressurized – Is a foreword regulated flow and pressure (preferred).
2) Flooded – Gravity induced flow and pressure (low PSI) (must use caution).
3) Suction – Lifting the fluid into the pump (least desirable, can easily cause cavitation. This type of system is used to have a 0 to minus head to induce chemicals into the pump).
Hose and Plumbing selection:
Material:
The hose must be flexible with a smooth I.D. (no ribs to cause cavitation or turbulence). The pressure rating should be at least 250 PSI working pressure. You should also make sure the hose does not swell a great deal under pressure or collapse under suction. Make sure the selected hose is compatible with the regional weather conditions (i.e. hot, cold, UV, etc.).
Diameter:
Again this will depend on your supply system. There is one basic rule: Never use a supply line small than the pump inlet (you can never be too large). With a pressurized system a 3/4” garden hose is sufficient to 7 GPM (depending on the pump being used and type of fluids being pumped), for some of the small pumps (to 3 GPM) you can use a 5/8” hose (depending on the pump being used and type of fluids being pumped).
One Note – any time you use a garden hose flush it out prior to each use. (They usually are dropped on the ground and will have dirt in the fitting)
On flooded inlet systems the hose diameter should be 1-1/2 to 2 times the inlet size. Flooded or gravity feed systems have very little pressure so you must rely on volume to the pump instead of pressure.
Fittings:
Keep the number of fittings to a minimum and try not to use 90° fittings. They cause turbulence and resistance. Only use full port fittings. Ball valves work the best for shut off valves make sure they are full port (never restrict upstream). Example: 45° elbow in 1 1/2” Ø= 1.9’ of straight pipe. 90° elbow in 1 1/2” Ø = 4.1’ of straight pipe.
Solenoid valves:
Most of these valves turn the fluid 270 degrees, be careful.
Upstream Injectors:
You must restrict the flow in order for them to work. You can starve and cavitate the pump quickly.
Pressure Gauges:
Install a Hg to + PSI gauge to monitor the inlet pressure.
Make sure all of the connections and threads are sealed and tight. If a fitting sucks air you will have cavitation in the system. A fitting sucking air will not always leak fluid.
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