Back to Articles
Easy Steps to Repair a KAPPA-40 Diaphragm Pump

Easy Steps to Repair a KAPPA-40 Diaphragm Pump

Posted by Sprayer Depot on

Replace the Diaphragm on a KAPPA-40 Diaphragm Pump

Spray Equipment Repair DIY How To Repair Video

Many of the repairs on spray equipment are fairly quick and easy to do yourself, saving you time and money. Replacing the diaphragm on a KAPPA-40 is no exception. The diaphragms are essential to optimally working diaphragm pumps, and they do wear out quickly with heavy use. Keeping these in good working order will ensure you are getting the most from your investment and help avoid costly breakdowns and downtime. 

The Sprayer Depot Video Library

The Sprayer Depot Video Library on YouTube is full of helpful how to videos, including several repair videos for common spray equipment, pumps and accessories. 

Sprayer Depot's Video Library on YouTube

KAPPA-40 Diaphragm Repair Video and Step-by-Step Directions


  • A screwdriver
  • Wrench
  • 1/2" socket
  • 11/16" socket
  • Diaphragm kit (2 diaphragms, 2 sets of O-rings and an air accumulator diaphragm)


  1. Loosen the bolts in one of the two head assemblies to remove it
  2. Remove the diaphragm nut and washer using the wrench
  3. Remove the diaphragm
  4. Remove the piston sleeve
  5. Drain the internal oil
  6. Loosen the bolts on the second head to remove it
  7. Perform steps 2-5 for the second head 
  8. Clean both sides of the pump with break cleaner
  9. Place the piston sleeve back in place in one of the two heads
  10. Place the diaphragm inside. The diaphragm has a beveled side which needs to be facing up
  11. Use the wrench to tighten the nut and washer back into place
  12. On each of the two head assemblies remove the inside valve assemble
  13. Replace the spring, valve seat (beveled side down), and large metal seat
  14. Replace O-ring with a new one
  15. The other valve assembly has the exact same parts but reversed (follow steps 13-14)
  16. Switch to the other head and perform steps 13-15 for this side as well
  17. Place the head assembly back in place on the side where you replaced the piston sleeve (step 9)
  18. Tighten bolts in a clockwise pattern to tighten evenly
  19. Switch to the other head and use non-detergent 40 weight pump oil to fill that open side
  20. Place piston sleeve back in place
  21. Clean up any excess oil
  22. Replace diaphragm, making sure that beveled side is facing up just like in step 13
  23. Use the wrench to tighten the nut and washer
  24. Place the head assembly back in place and tighten screws in clockwise pattern to tighten evenly   
  25. There is a clear bolt on the side of the pump and the oil level should be visible right in the center
  26. Remove the air accumulator head by loosening the bolts
  27. Once opened, remove the air accumulator diaphragm and replace with new
  28. Close everything back and tighten for a secure fitting

You are all done! Our customer service reps are available during normal business hours Monday through Friday. They are happy to help if you have questions about spray equipment or repairs, or need help locating replacement parts and kits.

Subscribe to the Latest News, Repair Videos & Helpful Information from Sprayer Depot

Blog Subscription:

Receive the latest blog posts, product announcements & company news direct to your inbox:

Sprayer Depot Video Library:

Be among the first to know when we release new repair videos, exclusive sprayer 360º video tours, new product releases and more - subscribe to Sprayer Depot's YouTube Channel:


NEW Product Line: Hose Reels by Kings Sprayers®

The #1 Choice for Quality Hose Reels

Kings Sprayers® has expanded and is now offering hose reels! These reels are proudly built by Kings Sprayers at Sprayer Depot's Orlando headquarters. They feature stainless steel inlet swivel and internal pipe, an aluminum frame that's lightweight and corrosion resistant, and a 2-year limited warranty. 

SHOP MODELS: Hose Reels by Kings Sprayers®

Sprayer Depot is committed to serving you!

Sprayer Depot specializes in spray equipment, parts and accessories for commercial use. Agriculture, horticulture, lawn & landscaping, and pest control industries, as well as theme parks/resorts/hotels, and golf & recreational facilities shop at Sprayer Depot. We ship worldwide. Kings Sprayers are proudly made in America at the Sprayer Depot headquarters in Orlando, Florida.

We appreciate your business, and look forward to assisting you again in the near future. Happy Spraying!

Related Posts

Comprehensive Guide to Wiring Pumptec's 12VDC Pumps
Read More
A step-by-step overview of the suggested wiring setup for Pumptec's 12VDC pumps, ensuring maximum performance, safety, a
5 Tips for Seasonal Sprayer Maintenance
Read More
Prepare spray equipment for cooler weather with these five tips for protecting your investment. Well-maintained equipmen
Sprayer Winterization
Read More
Follow the F.A.R.E.S. method for sprayer winterization, and your equipment will "fare" better through the idle winter mo

Subscribe to Our YouTube Channel for the Latest Repair Videos & Helpful Information from Sprayer Depot

NOW AVAILABLE: Lawn Trucks by Kings Sprayers®

The #1 Choice for Professional Sprayers Now Offers Professional Grade Lawn Trucks

Kings Sprayers® is expanding and now offers full sized lawn trucks. Contact us at or 800-228-0905, #2 to start designing your lawn truck.

Sign up through the button below to receive updates & the latest lawn trucks news.

Sprayer Depot Is Committed to Serving You!

Find us on Social Media