Water Pump On-Off Cycling FAQs

Short cycling pump due to closed valve
Water pressure tank removed entirely to fix short cycling?
Water leak at water tank air valve - a sign of waterlogged tank & short cycling cause

Water Leaks at the Water Tank Air Valve Q&A

Pump short cycles and water comes out of the air valve on the water tank

I checked the pressure in the bladder tank. When I checked it was 43psi but water came out as well. Shouldn't it only be air? On 2016-11-27 by Rick

Recommendations by (mod)

IF your tank uses an internal bladder (as you said) AND IF the air valve is mounted on the tank (not on water piping) THEN yes, if water comes out that suggests a leaky or torn internal bladder.

My photo here shows water leaking out at the air valve on a bladder-type water tank when I removed the little plastic cap that screws over the Schrader valve.

A water leak at the Schrader valve on a bladder type water pressure tank tells me that the bladder in this tank is burst or leaking.

The air valve for water pressure tanks that do NOT use an internal bladder may be located on an air volume control (AVC) on the tank or on piping at the bottom of the tank or less common, at the tank top.

For air valves (Schrader valves) at or near the top of these tanks if water comes out of the valve when you depress the valve's center pin then the tank has lost its air charge or an AVC float control is not working and is not keeping enough air in the tank.

Pump runs for about 2 seconds and then shuts down - how do I use the air valve to see if there's air in the tank?

My pump runs for about 2 seconds and then shuts down. It turns on about every minute or so.

an I test the air pressure by pushing the pin on the air inlet valve? If water comes out is that an indication of no air pressure? And should air be leaking out when I press that pin? The tank does build up pressure if no water is used for awhile.

The short cycles will eventually build pressure, but obviously doesn't hold because the pump will only run for about 2 seconds, regardless if the water is running or not.

Both the tank and the switch aren't that old. Maybe 4-5 years, 6 at the most. On 2016-09-03 by Anonymous

Explanation by (mod)

Yes, pressing the center pin in the Schrader valve on a water pressure tank will release either air or water at that point.

If water comes out of an air valve on the tank itself then the tank is waterlogged or if it's a bladder type tank the bladder has probably leaked or burst.

Water pump is cycling on and off every 2-3 sec. - traced to closed valve

My water pump is cycling on and off,every 2-3 sec. when a tap is opened. I have replaced the switch with a 20-40 psi switch and checked that the pressure tank ( bladder type ) has 18 psi in it.. any ideas would be helpfull. Tks On 2015-08-10 by Dave

by (mod) - look for a closed or blocked water valve

Dave:

I'd be looking for an obstruction such as a nearly closed or blocked valve.

But even better, watch the pressure switch. It's possible that water is not entering the tank (closed or broken valve) or that your tank is waterlogged and includes a pressure gauge that's stuck, giving a false reading.

Gently rock the tank (don't break any connections) and you can usually tell if it's empty (it'll be light), and similarly, if no water is entering the tank its pressure and temperature and weight wont' change.

by Anonymous - the gate valve had come off the stem - I replaced it and the problem is fixed

Thank you I checked the gate valve and found the gate had come off the stem. I replaced it with a ball valve, No more problems.I will be telling my frends about this site.

by (mod)

Very good going, Dave, that problem can be tough to find.
A gate valve knob will spin and it's not always obvious if the velve internal body is moving or not.

Thanks so much for the feedback, that will help other readers. I'll be sure to merge your finding into our tips.

DF

Do I need a water pressure tank at all?

I have had problems with water supply system so I ended up doing away with the header tank entirely; I just and pressurised the system directly to the house.

The system ran fine for quite a while but is now constantly short cycling.

I removed the bladder tank and blocked off the fitting.

Again the pump ran fine for a while but now back to short cycling again. Was it a mistake to pressurise directly to the house and shoul;d I reinstate the header tank? - (July 5, 2015) Mike Lambadarios

Reply: You need to either install a water pressure tank or install a pressure-sensitive water pump system.

MIke

Pressure-sensitive water pumps

You need either a pressure tank installed to prevent short cycling of the pump, or you need a special hydropneumatic pump control that combines the pump with a pressure switch - shown at left. This is essentially is a switch that can turn a pump on and off when needed without short cycling.

In our photo at left that silver domed gadget above the red pressure-sensitive water pump works with the silver micro-pressure tank to provide a boost to water delivered (typically) from a rooftop water tank. No water pressure tank is used with this system.

These systems are typically used as water pressure boosters and not as the primary water source pump.

The little silver dome dome is a miniature pressure tank itself, pre-charged to 7 psi and the whole system is calibrated to avoid short cycling of the water pump.

This equipment is distributed by bombasrowa.com and is widely distributed in Mexico where often we want simply to boost the pressure delivered by a rooftop water storage tank. Keep in mind that the total flow rate and building water service from this sort of system is of limited capacity.

Often we see pressure sensitive water pumps or inline pump controllers used with rainwater harvesting systems and cisterns or rooftop water tank systems serving small buildings. Submersible models of these pumps are also available for installation in the water tank.

Similar devices are sold by Aqua Group in India: the Aquatex APS hydropneumatic system. This approach floats a very small internal-bladder type pressure tank atop the water pump. Other models are used in marine applications such as the Shurflo and the Jabsco.

Inline pump controllers to avoid using a pressure tank

A third option might be to use an in-line pump controller. An inline pump controller can be added to an existing system and works with most water pumps. The inline pump controller senses pressure changes similarly to the pressure-sensitive water pump system we described above, and turns the pump on or off as needed.

Some inline pump controllers include an additional sensor to shut off the pump if the water supply is lost, thus protecting the pump from damage.

Pressure sensitive pump references & sources

• Arnette, Henry K. "System for protecting a liquid pump." U.S. Patent 5,244,351, issued September 14, 1993.
• AQUASUB ENGINEERING (Corporate Office) Thudiyalur (post) Coimbatore - 641 034. Tamilnadu, India Phone: 0422-2642484 Fax : 0422-2642128 Email : aquasub@vsnl.com
• Bynum, J. "Pressure sensitive control for pump regulator." U.S. Patent 3,794,789, issued February 26, 1974.
• Bell & Gossett: commercial grade and sized inline pumps, http://bellgossett.com/pumps-circulators/in-line-pumps/
• e-LNE in-line pumps, capable of higher flow rates than the small systems we discussed in the article above,Xylem Water Solutions UK Limited Main Office Millwey Rise Industrial Estate Axminster Devon EX13 5HU – UK Tel: (+44) 01297 630210 Fax: (+44) 01297 630295 E-mail: lowaraukservice@xyleminc.com http://www.lowara.co.uk/
• Grundfos high efficiency in-line pumps: http://net.grundfos.com/Appl/WebCAPS/Grundfosliterature-3847.pdf
• Rainwater Harvesting Ltd Unit A Harrier Park Southgate Way Peterborough Cambridgeshire PE2 6YQ General enquiries call +44 (0) 1733 405 111 Fax: 01733 230 996 info@rainwaterharvesting.co.uk