2″ CH&E Replacement Diaphragm – Neoprene

The CH&E 2 Inch Neoprene Replacement Diaphragm P2331N is a diaphragm for CH&E 5400 and 6400 series 2 inch pumps. The CH&E parts manual lists part number P2331 as the diaphragm for both the 5400 aluminum build and the 6400 cast iron build. Each pump uses one. Before you order, check the model and serial number on your pump nameplate. Compare your old diaphragm as well. Ken’s Distributing can help you review fitment if you are not sure.

Key Product Highlights

• Manufacturer part number P2331. Neoprene variant P2331N.
• Fits CH&E 5400 series aluminum and 6400 series cast iron 2 inch pumps, as listed in the CH&E parts manual.
• Neoprene compound.
• For 2 inch nominal pump size. This is the pump port size, not the diaphragm width.
• One diaphragm per pump.
• Matching neoprene rebuild kit is W103-020.0N.
• Check your pump model and serial number before ordering. Other models may need verification.

Specification Table

About the CH&E 2 Inch Neoprene Replacement Diaphragm

This flexible neoprene component creates the pumping action inside the pump. It works between the pump frame and water box as the connecting mechanism moves through each stroke. It sits between the pump frame and the water box. When it wears out, the pump loses prime, loses stroke, or stops moving water well.

The CH&E parts manual for 2″ gas engine pumps lists part number P2331 as the diaphragm. Your pump uses one.

Neoprene is one of several compounds this diaphragm is made in. CH&E also lists rubber, Buna-N, TPE and Viton versions of the same part. Select the diaphragm compound based on the original pump configuration, the fluid being pumped, and the manufacturer’s material guidance. Do not change compounds based on appearance alone.

Part number P2331 and P2331N

The CH&E parts list shows P2331 as item 15 in the 2 inch pump breakdown. The same number is used for both the 5400 aluminum pump and the 6400 cast iron pump.

CH&E adds a letter to the end of the number to show the compound. The N on P2331N means neoprene. You may see the base number P2331 on older paperwork or on a parts diagram. Both point to the same item 15 in the parts list.

If your old part is stamped with a different number, send it to us before you order. We will check it against the CH&E parts list.

Which pumps this diaphragm fits

The CH&E manual lists P2331 for these 2 inch gas engine powered diaphragm pumps:

• CH&E 5400 series, aluminum
• CH&E 6400 series, cast iron

Individual model numbers in these series include 5401, 5402, 5403, 5405, 6401, 6402, 6403 and 6405. Confirm your model before you order.

Some Magnum or Mud Hog pumps may use related CH&E-style components. Fitment is not confirmed on this page. Contact Ken’s Distributing with the model and serial number for review.

Do not order by how the part looks. Two diaphragms can look the same and still fit different pumps.

How to confirm this diaphragm fits your pump

Follow these four steps before you order.

1. Find the nameplate on your pump. It lists the model number and the serial number. The CH&E manual asks you to write both down before ordering any part.
2. Check that your pump is a 2 inch. The 2 inch is the port size on the pump, not the width of the diaphragm.
3. Look at your old diaphragm. Note the outside diameter, the thickness, and how many holes it has.
4. Check the old part for a stamped number. Compare it to P2331.

If any step does not match, stop and contact us.

Installing the diaphragm

The CH&E manual gives these steps for 2 inch pumps.

Turn the connecting rod to the down position. Take out the four bolts that clamp the diaphragm between the pump frame and the water box. Take off the three nuts that hold the diaphragm to the diaphragm bottom plate.

Fit the new diaphragm onto the studs and the bottom plate. Use a pipe spacer over the studs to seat it. Put the assembly back on the connecting rod.

Tighten the three nuts to 34 to 40 N-m, which is 25 to 30 lb-ft. Center the diaphragm over the water box. Clamp it with the four bolts in a crossing pattern and use the same torque.

Parts to check at the same time

While the pump is open, look at these parts. The CH&E 2 inch parts list covers all of them.

• Flap valve assembly, SA-10003N in neoprene
• Diaphragm bottom plate, P3353
• Retaining washers, P3360, two per pump
• Connecting rod, P3352

If several of these are worn, the neoprene rebuild kit W103-020.0N may be a better buy than single parts.

Common ordering mistakes

• Ordering by pump port size alone. A 2 inch port does not mean every 2 inch diaphragm fits.
• Matching by looks. Compare numbers and measurements instead.
• Skipping the serial number. Some pumps changed during their production run.
• Mixing up P2331 and a similar looking number. One digit changes the part.
• Ordering one compound when the job needs another.

Need help with fitment

Send us your pump model number, your serial number, and the number stamped on your old diaphragm. Ken’s Distributing will check it against the CH&E parts list and tell you which part you need. Call (303) 699-7845 or email us.

Frequently Asked Questions

What pumps does part number P2331 fit?

P2331 is listed in the CH&E parts manual as the diaphragm for 2 inch gas engine powered pumps in the 5400 aluminum series and the 6400 cast iron series. The same number covers both builds. Model numbers in these series include 5401, 5402, 5403, 5405, 6401, 6402, 6403 and 6405. Other pumps may use a different part. Check the model and serial number on your pump nameplate before you order. If your pump is not on this list, contact us and we will check it for you.

Is P2331 the same as P2231?

No. P2331 is the number printed in the CH&E parts manual for the 2 inch diaphragm. P2231 is a different string of digits. You may see it on parts lists or older paperwork, including some pages on this site that we are correcting. If your paperwork shows P2231, do not assume it is the same item. Send us the number you have along with your pump model, and we will check it against the CH&E parts list before you buy.

What does the N mean in P2331N?

The letter at the end shows the compound. N means neoprene. CH&E uses the same base number with different letters for different materials. You will see B for Buna-N, R for rubber, V for Viton and TPE for the TPE version. So P2331N and P2331R are the same shape of part in two different compounds. Pick the compound that suits what you pump. If you are unsure which compound your pump had, contact us with your model number.

Is the 2 inch measurement the size of the diaphragm?

No. The 2 inch is the port size on the pump, which is where the hose connects. The diaphragm itself is wider than 2 inches. This is the most common ordering mistake we see. Do not measure your old diaphragm and look for a part with that number of inches in the name. Instead, match the pump model, then compare your old part to the listed part number. Measure the old diaphragm only to double check the fit.

How do I confirm this diaphragm fits my pump?

Start with the nameplate on your pump. It shows the model number and the serial number, and the CH&E manual asks you to record both before ordering parts. Next, take out your old diaphragm and look for a stamped part number. Compare it to P2331. Then measure the outside diameter and thickness of the old part and count the holes. If every check lines up, the part fits. If any check does not, contact Ken’s Distributing before you order.

What torque should I use when I install this diaphragm?

The CH&E manual gives 34 to 40 N-m for 2 inch pumps, which is 25 to 30 lb-ft. First on the three nuts that hold the diaphragm to the diaphragm bottom plate. Then on the four bolts that clamp the diaphragm between the pump frame and the water box. Tighten those four in a crossing pattern so the clamp is even. Uneven clamping can make the diaphragm leak or tear early.

When should I replace the diaphragm?

Replace it when you find a break or a leak in it. The CH&E troubleshooting guide lists a damaged diaphragm as one reason a pump will not prime or will not run properly. Other signs are a drop in flow, a loss of stroke, or water where it should not be. Service life depends on what you pump and how many hours the pump runs, so we do not give a set replacement interval. Check the diaphragm each time you service the pump.

Which other parts should I check while the pump is open?

Check the flap valve assembly, part SA-10003N in neoprene. Also look at the diaphragm bottom plate P3353, the two retaining washers P3360, and the connecting rod P3352. These parts sit next to the diaphragm and wear at a similar rate. If more than one is worn, the neoprene rebuild kit W103-020.0N may cost less than buying the parts one at a time. Ask us and we will tell you which option suits your pump.