A surface pump drawing from a tank, dam or sump runs fine on day one. A few weeks later the customer rings. The pump runs but won't deliver, and every time you're out there you're re-priming it.
The fix is nearly always at the bottom of the suction line: a foot valve that holds the water column, and a strainer that keeps rubbish out of it.
Zetco's new range gives you 316 stainless foot valves from 15mm to 250mm, plus three kinds of suction basket. Here's how to set it up.
What a Foot Valve Does
A foot valve is a non-return valve that sits at the very bottom of the suction pipe, under the water. When the pump stops, the foot valve closes and holds the column of water in the suction line, so the pump stays primed for the next start.
Without one, the water drains back down the suction line every time the pump stops, and the pump runs dry trying to pull it back up.
Most foot valves also carry a strainer to keep sticks, leaves, sediment and frogs out of the valve and the impeller.
Threaded 316 Foot Valve: 15–50mm
The Zetco 4023 2-piece stainless foot valve is the one for most domestic and light commercial suction lines.
- 316 stainless body, disc and strainer
- Female BSP, 15–50mm
- Listed at 6300 kPa, -20°C to 170°C
Why stainless? Foot valves live permanently underwater, often in tank water, bore water or dam water that's anything but neutral. Brass and plastic foot valves corrode, crack or clog, and they're hard to service without pulling the whole line.
316 lasts, and it's the obvious choice on bores and corrosive or brackish sources.
Flanged 316 Foot Valve: 50–250mm
For bigger pumps, the Zetco 4024 flanged foot valve goes up to 250mm.
- 316 stainless body, NBR seal, integral strainer
- Flanged connection, 50–250mm
- Listed at 1900 kPa @ 37°C
It suits irrigation, dam and river offtakes, fire service suction from tanks, and large transfer pumps where a threaded valve at that size isn't practical.
Neither foot valve is WaterMarked. Zetco lists both as not for installations that must comply with AS/NZS 3500, so they're for non-potable suction duties.
Suction Baskets: Add or Replace a Strainer
Sometimes you just need a strainer on the end of a suction pipe, or a replacement basket for a foot valve whose screen has given up. There are three options.
- Stainless basket, nylon thread (1520), 10–100mm. Cheapest, with no corrosion at the thread, but nylon threads can strip if over-tightened or serviced often.
- Stainless basket, brass thread (1521), 10–100mm. A stronger thread for larger or frequently serviced suction lines.
- All-316 basket (4022), 15–50mm. Basket, mesh and thread are all 316, for corrosive water, chemical transfer and marine suction where nylon or brass would degrade.
These are suction strainers, not pressure-rated parts. They go on the suction end only.
Install Tips That Save a Callback
- Keep it off the bottom. Suspend the foot valve clear of the tank or sump floor so it doesn't suck up sludge.
- Keep it well submerged. If the water level drops near the inlet, the pump draws air and loses prime anyway.
- Size it to the suction pipe, not the pump outlet. An undersized foot valve chokes the suction and starves the pump.
- Seal every suction joint. A pinhole air leak above water stops the pump priming just as surely as a failed foot valve.
- Make it serviceable. On deep tanks and bores, plan how you'll lift it out. Screens need cleaning.
Choosing Quickly
- Tank or bore pump, up to 50mm suction: 4023
- Irrigation, dam offtake or fire service suction, 50–250mm: 4024 flanged
- Replacement screen, general use: 1520 nylon or 1521 brass thread
- Corrosive or chemical suction: 4022 all-316
The Short Version
A foot valve keeps the prime and a strainer keeps the rubbish out. In 316 they last underwater where brass and plastic don't.
Browse the range in Foot Valves & Y Strainers and Zetco. For the pump itself, see submersible vs surface pumps. For check valves on the discharge side, see check valves compared.
Frequently Asked Questions
Why does my pump keep losing prime?
Usually a failed or missing foot valve, a blocked strainer, or an air leak on the suction side. Check the foot valve seals, clean the screen, and make sure every suction joint is airtight.
Where does a foot valve go?
At the bottom of the suction pipe, submerged in the water source. Suspend it clear of the floor so it doesn't draw in sludge.
Can I use these foot valves on drinking water?
Zetco lists the 4023 and 4024 as not WaterMarked, so they're not for installations that must comply with AS/NZS 3500.
Nylon, brass or 316 thread on a suction basket?
Nylon for low-cost general use, brass for a stronger thread on larger or frequently serviced lines, and all-316 for corrosive, chemical or marine suction.