A cautious "Yes" to the question "Can I feed this type of pump with mains water pressure?". However, you MUST supply the mains water through a pressure reducer/regulator. On a European touring caravan with a Whale Watermaster inlet socket (through which the pump normally lifts water from an outside container such as a 40 litre Aquaroll or 50 litre Water Hog) you can use the Whale "Aquasource" mains connector. This limits the delivered pressure to about 1 Bar (if I remember correctly) and is said by Whale (Munster Simms of Belfast, Northern Ireland) to regulate mains pressure up to 5 bar.
However, if your Shurflo RV pump is horizontally mounted, with the ports also horizontal, it may be prone to trapping air in the top of the upper lobe of the pumping chamber. This may cause the pressure sensor to behave erratically when the pump should shut off cleanly. Fresh mains water may be more aerated than water which has stood for a while in an outside container, so direct mains water may worsen this problem. To avoid this on a pitch with its own mains water tap, use your Aquaroll/Water Hog as normal but fit into the "side" filler hole an automatic filler unit (a small ball valve device with its own pressure reducer). This connects by hose to the tap and keeps the container at a constant c.50% full. This is a much less compact solution than using an Aquasource adaptor, but may be preferable if the pump is prone to hesitating and bumping on and off when it should shut off cleanly (and to irregular cycling when delivering a small flow).
Do not blame the accumulator for such problems! If this is the air-pressurised type, provided the bladder is inflated to well under the pump pressure switch's cut-off pressure this tank should do its job of allowing the pump to cycle at a low frequency when the outlet flow is restricted by, for example, turning a tap (faucet) down to a reduced flow. It should also give a fairly smooth and unvarying flow during this cycling. If the cycling is irregular and bumpy, wonder about air trapped in the pump head. If the pump stays on when pressure is at or over the maximum allowed by the pressure switch setting, or won't turn on when the pressure falls, look to the electrical microswitch which the pressure sensor operates. On our Shurflo SUK-022A pump (a European model) this microswitch is made by Omron and is easily available from web traders such as Mouser Electronics (www.mouser.com).
The accumulator is also intended to act as a surge damper while the pump is running, so the water flow does not pulsate and the pump knock or hammer. I have found it necessary to run the accumulator bladder at only about 3 psi for it to do this job smoothly. Yet, even with so little pressure in its bladder, it still allows the pump to operate on a satisfactorily long on/off cycle when the tap you are using is only partly open. It still allows the pump to run for a measurable amount of time after a tap is closed, and for a reasonable amount of water to be delivered after you open a tap before the pressure drops enough for the pump to start.
Does anyone know if installing this type of pump vertically, with the pump head at the bottom so it is more or less always guaranteed to fill with water and not trap air, is effective at dealing with erratic/irregular pressure sensor operation? Reducing the operating pressure by screwing out the adjuster screw seems to help, but must reduce the flow rate.
Carl, February 2010
