Solving Diaphragm Pumps Problems 


Here you will find a list of typical problems with air operated diaphragm pumps. Even though diaphragm pumps are robust and can be used in almost any application, they still do find a way to cause issues. Most of these problems are either an operator issue or from wearing out over time. 

If you have trouble finding your issue, please do not hesitate to contact us. 




Pump cycles at stall or fails to hold pressure at stall.

Worn check valve balls, seats or o-rings.

Replace valve balls, seats or o-rings.

Pump will not cycle, or cycles once and stops.

Air valve is stuck or dirty.

Disassemble and clean air valve. Use filtered air.

Check to see if the valve ball is severely worn and/or wedged in seat or manifold.

Replace ball and seat.

Check to see if the valve ball is wedged into seat, due to over pressurization.

Install Pressure Relief Valve.

Dispensing valve clogged.

Relieve pressure and clear valve.

Pump operates erratically.

Clogged suction line.

Inspect; clear.

Sticky or leaking balls.

Clean or replace.

Diaphragm (or backup diaphragm) ruptured.

Replace diaphragms.

Restricted exhaust.

Remove restriction.

Pilot valves damaged or worn.

Replace pilot valves.

Air valve damaged.

Replace air valve.

Air valve gasket damaged.

Replace air valve gasket.

Air supply erratic.

Repair air supply.

Exhaust muffler icing.

Use drier air supply.

Air bubbles in fluid.

Suction line is loose.








Diaphragm (or backup) ruptured.

Replace diaphragms.

Loose inlet manifold, damaged

seal between manifold and seat, damaged o-rings.

Tighten manifold bolts or replace seats or o-rings.


Loose diaphragm shaft bolt.

Tighten or replace.

Damaged o-ring.


Diaphragm shaft bolt o-ring damaged.

Replace o-ring.

Pump cavitation.

Reduce pump speed or suction lift.

Fluid in exhaust air.

Diaphragm ruptured.



Loose fluid side diaphragm plate

Tighten or replace.

Pump air valve freezes.

(talk to us about non-freezing air valves/exhaust)

Excessive moisture in compressed air.

Install a dryer or hot air generator for compressed air. Alternatively, a filter may be used to remove the water from the compressed air in some applications.

Pump exhausts excessive air at stall.

Worn air valve block, o-ring,

plate, pilot block, u-cups, or pilot pin o-rings.

Inspect; replace.


Worn shaft seals


Pump leaks air externally.

Air valve cover or air valve cover screws are loose.

Tighten screws.



Air valve gasket or air cover gasket is damaged.

Inspect; replace.


Air cover screws are loose.

Tighten screws.

Pump leaks fluid externally from ball check valves.

Loose manifolds, damaged

seal between manifold and seat, damaged o-rings.

Tighten manifold bolts or replace seats or o-rings.


Pump cycles but will not prime.

Pump is running too fast, causing cavitation before prime.

Reduce air inlet pressure.







Check valve ball severely worn or wedged in seat or manifold.

Replace ball and seat.

Seat severely worn.

Replace ball and seat.

Outlet or inlet clogged.


Inlet or outlet valve closed.


Inlet fittings or manifolds loose.


Manifold o-rings damaged.

Replace o-rings.

Premature diaphragm failure


Enlarge pipe diameter on suction side of pump or move closer to the product





Excessive flooded suction pressure

Move pump closer to the product; raise pump/place pump on top of tank to reduce inlet pressure

Misapplication (chemical/physical incompatibility)

Consult chemical resistant guide for compatibility for the products, cleaners and temperature limitations

Incorrect diaphragm plates or plates backwards

Check operation manual for correct part installation

Start up with full pressure

Recommend to start up pump slowly

Unbalanced Cycling

Excessive suction lift.

For dry lifts or self-priming from dry, filling the chambers with liquid will prime the pump in most cases







Undersized suction line.

Meet or exceed pump connections.

Pumped fluid in air exhaust muffler

Disassemble pump chambers. Inspect for diaphragm rupture or loose diaphragm plate assembly.

Suction side air leakage or air in product.

Visually inspect all suction-side gaskets and pipe connections

Check valve obstructed.

Disassemble the wet end of the pump and manually dislodge obstruction in the check valve pocket.

Check valve and/or seat is worn or needs adjusting.

Inspect check valves and seats for wear and proper setting. Replace if necessary.

Entrained air or vapor lock in chamber(s)

Purge chambers through tapped chamber vent plugs.


Global Pumps was established in 1977, after the need for a versatile and customer service oriented industrial pumps supplier in the market was identified. More than 35 years on, the team at Global Pumps continues to grow and develop new ways in which to effectively fulfil this mission statement.

Global Pumps: Australia's Trusted AOD Pumps Supplier

Contact us today about our premium quality diaphragm pumps for sale, or check out our other great products including conductive diaphragm pumps,  food grade peristaltic hose pumps and 5 things to check when your pump doesn't work.


Guide To Selecting the Best Pump

If you need some guidance on how to select the right pump then you’re not alone! There’s such a wide range of pumps in Australia, from centrifugal pumps to hose pumps to diaphragm pumps. The options available to you can make it a difficult choice, so we’ve created this special guide to help step you through the process of selecting the ideal pump for your requirements.

Enquire here for more information or to request a quote: