Jef, this is from a Shur Flow Brochure:
● SHURflo recommends at least 1ft. [.3 M] of ½" [13mm] I.D. flexible high pressure tubing to both ports. Ideally the pumps ports/strainer should not be connected to plastic or rigid pipe. The pump's normal oscillation may transmit through rigid plumbing causing noise, and possibly loosen or crack components.
● Installation of a 50 mesh strainer (SHURflo P/N 170) is recommended to prevent foreign debris from entering the pump.
● SHURflo swivel barb fittings provide easy removal if maintenance or access is required.
The fittings are designed with a "taper-seal", creating a water tight connection when handtightened.
Never use Teflon tape or sealing compounds on threads. Sealer may enter the pump causing a failure. Failure due to foreign debris is not covered under warranty.
Always secure barb tubing connections with properly sized stainless steel clamps to
● Rapid cycling may be caused by excessive back pressure created by one or more of the
following within a plumbing system:
Water filters not on separate feed lines.
Flow restrictors in faucets and shower heads.
Small I.D. lines. Pipe/tubing should be at least ½" [13mm] I.D. for main lines.
Restrictive fittings and connections (elbows, "T's", feeder lines to faucets, etc.)
Restrictions in a plumbing system may cause the pump to rapid cycle (ON/OFF within 2 sec.) during low flow demands. Cycling should be minimized to prevent pulsating flow, and to achieve maximum pump life.
To determine if adjustment is necessary, turn a faucet ON to lower than average flow of water.
The pump should cycle, but its "OFF time" must be 2 sec. or longer. If the cycling is correct, leave well enough alone. If the pump is cycling rapidly increase the setting by turning the screw clockwise (1½ turn MAX.) until the pump operates for 1 sec. with at least 2 sec. "OFF time". If cycling cannot be minimized consider removing plumbing restrictions or simply install a SHURflo Accumulator.
Vibration induced by road condition can cause plumbing or pump hardware to loosen. Check for system components that are loose. Many symptoms can be resolved by simply tightening the hardware. Check the following items along with other particulars of your system.
PUMP WILL NOT START/ BLOWS CIRCUIT:
connections, fuse or breaker, main switch, and ground connection.
● Is the motor hot? Thermal breaker may have triggered; it will reset when cool.
● Is voltage present at the switch? Bypass the pressure switch. Does the pump operate?
● Charging System for correct voltage (±10%) and good ground.
● For an open or grounded circuit, or motor; or improperly sized wire.
● For seized or locked diaphragm assembly (water frozen?).
WILL NOT PRIME/SPUTTERS: (No discharge/Motor runs)
● Is the strainer clogged with debris?
● Is there water in the tank, or has air collected in the hot water heater?
● Is the inlet tubing/plumbing sucking in air at plumbing connections (vacuum leak)?
● Is inlet/outlet plumbing severely restricted or kinked?
● Proper voltage with the pump operating (±10%).
● For debris in pump inlet/outlet valves or swollen/dry valves.
● Pump housing for cracks or loose drive assembly screws.