Frequently Asked Questions

Have questions about Wilden Diaphragms?
We have answers!


How does a diaphragm pump operate?

A diaphragm pump draws fluid into an expanding cavity, and then displaces that fluid as the cavity is constricted.

What is a diaphragm and what does it do?

A diaphragm is a flexible membrane that separates the driving fluid, typically compressed air, from the driven fluid in a diaphragm pump. Movement of the diaphragm creates the expanding and contracting cavities within a diaphragm pump.

What is an elastomer?

Elastomer is a common term to describe diaphragms, balls, valve seats and wet end gaskets.

What types of diaphragms does Wilden offer?

Wilden offers over 150 diaphragm products to optimize AODD pump performance and to fully address any customer’s application around the world:
  • Nylon fabric reinforced-rubber diaphragms in four material options (Neoprene, Buna-N, EPDM and Viton®) and two stroke configurations (Traditional “Pie” shaped and Ultra-Flex™ convolute diaphragms).
  • Thermoplastic Elastomer (TPE) diaphragms in four material options (Polyurethane, Wil-Flex™, Saniflex™ and Geolast®) and two stroke configurations (Traditional “Pie” shaped and EZ-Install convolute diaphragms).
  • Two-piece PTFE/Elastomer over-lay assembly diaphragms in two stroke configurations: Reduced-Stroke PTFE and Full-Stroke PTFE. Each are offered with several back-up diaphragm materials including Neoprene, Buna-N, EPDM, Saniflex, and Wil-Flex.
  • Integral Piston (IPD) diaphragms for sanitary and clean-in-place (CIP) installations: Reduced-Stroke PTFE laminate diaphragm and Full-Stroke Wil-Flex (food-grade Santoprene) diaphragm.

Are Wilden Diaphragms the best choice for Wilden AODD pumps?

Yes. Wilden diaphragms are engineered to optimize the performance of Wilden AODD pumps. With the largest selection of AODD pump diaphragms in the world – 300% more than competitors – Wilden ensures that your unique application is fully met with the best possible diaphragm, ranging from aggressive fluids to petroleum/oils to seawater. Wilden’s legendary quality ensures superior construction and engineering for long flex life and superior durability. In addition, with a distribution network of over 300 distributors around the world, you are sure to get the service, support and replacement parts you need to keep your operation running at peak performance.

NOTE: Using non-Wilden diaphragms voids the Wilden AODD pump warranty. Genuine Wilden – Accept Nothing Less

Will using a non-Wilden diaphragm void my pump warranty?

Yes, Wilden diaphragms are designed to fit with Wilden AODD pumps; using non-Wilden diaphragms will void the pump warranty.

What do the colored dots on the air side of the diaphragms denote?

The various colored dots denote what material the diaphragm is made of.

Why do some diaphragms have two colored dots?

The two dots represent FDA-approved material.

Should I always use “A” rated diaphragms?

In most cases - Yes. Contact your Wilden distributor or use the Ask a Question of the Diaphragm Expert on this site to find out when a “B” rated diaphragm is an acceptable substitute or when price is the driving factor.

  1. Neoprene or Wil-Flex™ diaphragms should generally be used unless the chart shows them to be unsatisfactory. Even though Buna-N, EPDM and Viton® may show "A" ratings, if neoprene or Wil-Flex™ have at least a "B" rating, it will probably be the most economical choice on a "cost of diaphragms per gallon pumped" basis.
  2. This is especially true when considering the use of Viton® diaphragms due to their replacement cost being over six times (x6) that of neoprene. Viton® should only be considered for aggressive media at extreme temperatures if it shows an "A" rating and neoprene, Buna-N and EPDM show an unsatisfactory rating.

What are the advantages of using the EZ Install?

 Material Part Number  Pump Designer
Geolast  XX-1022-15 ZGS
Polyurethane  XX-1022-50 ZPS
Saniflex (Hytrel)  XX-1022-56 ZSS
Wil-Flex (Santoprene)  XX-1022-58 ZWS 
Wil-Flex (Santoprene) food-grade   XX-1022-57 FWS 

Features and Benefits:

  • Convolute shape - diaphragm inversion not required for assembly
  • Uses existing rubber and TPE shafts and hardware
  • Equivalent performance and durability
  • New Geolast material option equivalent to nitrile (Buna-N) at a lower cost

What are the advantages of using the Full-Stroke PTFE?

Product Features and Benefits:
  • Full Stroke PTFE with Wil-Flex™- or Saniflex™-backup
  • Superior flow rates and increased suction lift
  • Simplified inventory (uses existing Rubber or TPE shaft and piston assemblies)
  • Temperature limits 4.4°C (40°F) to 104°C (220°F)
  • Retrofit-able to all 25 mm (1”) through 76 mm (3”) Wilden pumps
Other Considerations:
  • TWS = Full-Stroke PTFE with Wil-Flex™-backup
  • TSS = Full-Stroke PTFE with Saniflex™-backup
Pricing Considerations:
  • Primary PTFE diaphragm is the same list price as existing PTFE diaphragm
  • TPE backup diaphragms are the same list price as existing Neoprene backups

How can I determine what is the best diaphragm for my operation?

Start by identifying the following: 1) your Wilden pump, 2) what fluids your operation is pumping, and 3) what fluids your operation is using to clean the piping system. Then reference the Wilden Cross Reference Grid and identify your fluid column. Next determine other factors such as desired flex life, abrasion resistance, and temperature parameters. The Grid will provide recommendations that you’re your operation’s application. Select the diaphragm that best meets the application and fits within the target budget.

Due to the unique parameters surrounding every pump application, it is always best to contact your Wilden distributor, or to utilize the Ask a Question of the Diaphragm Expert on this site.

What is Wil-Flex™?

Wil-Flex is a trade name for Santoprene. It is a thermo-plastic elastomer (TPE), combining Polypropylene and EPDM rubber. Wil-Flex diaphragms provide superior flex life and abrasion resistance over fabric reinforced rubber diaphragms.

What is EPDM?

EPDM stands for Ethylene Propylene Diene Monomer. Nordel™ is Dow Chemical’s trademarked name for their EPDM offering. EPDM exhibits satisfactory compatibility with fireproof hydraulic fluids, ketones, hot and cold water, and alkalis, and unsatisfactory compatibility with most oils, gasoline, kerosene, aromatic and aliphatic hydrocarbons, halogenated solvents and concentrated acids.

What is NBR?

Nitrile Butadiene Rubber (NBR) also known as Nitrile Rubber, and Buna-N, among others. This is a synthetic rubber generally resistant to oil, fuel and other chemicals. Used in the automotive and aeronautical industries to fuel and oil handling items.

Why does PTFE need a back-up diaphragm?

PTFE has no shape memory; it will stretch but will not return to shape as a rubber diaphragm will. Teflon® requires a backing elastomer to spread the force of air pressure evenly across the diaphragm surface to keep it from ballooning out of shape and potentially bursting.