3″ CH&E Replacement Diaphragm – Rubber

The CH&E 3 Inch Rubber Replacement Diaphragm P2726R replaces the diaphragm in CH&E 5500 and 6500 series pumps. The CH&E parts manual lists P2726 as item 15 for both the 5500 aluminum and the 6500 cast iron build. Your pump uses one. If your old part has no number on it, measure it and check your pump nameplate. Ken’s Distributing will match it against the CH&E parts list for you.

Product Highlights

• Manufacturer part number P2726, item 15 in the CH&E 3 inch parts list. Rubber variant P2726R.
• Fits CH&E 5500 series aluminum and 6500 series cast iron 3″ pumps.
• Rubber compound. The same base part is also listed in neoprene, Buna-N, TPE and Viton.
• Multiquip lists the same number, P2726, for the Polyquip pump.
• One diaphragm per pump.
• Matching rubber rebuild kit is W103-030.0R.
• Send us a photo and a measurement if your old part has no number on it.

Specification Table

Not sure which diaphragm you have? Start here

Work through these in order. Stop at the first one that gives you an answer.

1. Is there a number stamped on the old part? If it reads P2726, this is your part. If it reads P2726 with a letter after it, the letter is the compound. R is rubber.
2. Does your paperwork name a different pump? Multiquip catalogues list P2726 as a diaphragm for the Polyquip pump. If you bought through an equipment dealer, your invoice may use that name for the same number.
3. What does the pump nameplate say? The CH&E manual asks you to record the model number and the serial number before ordering any part. A model starting with 55 is the aluminum build. A model starting with 65 is the cast iron build. Both use the same diaphragm.
4. Still nothing? Measure the old diaphragm across its widest point. Measure the thickness. Count the holes. Photograph both faces. Send all of that to us with your pump model, and we will match it against the CH&E parts list.

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

About the CH&E 3 Inch Rubber Replacement Diaphragm

This is the flexing part that drives water through the pump. It sits between the pump frame and the water box. When it splits or leaks, the pump stops priming, loses stroke, or stops moving water.

The CH&E parts manual lists it as item 15, number P2726, for 3″ gas engine powered pumps. Your pump uses one.

Rubber is one of five compounds listed under this base number. The others are neoprene P2726N, Buna-N P2726B, TPE P2726TPE and Viton P2726V. The shape is the same across all five, so switching compound does not change how the part mounts.

A distributor catalogue for the CH&E pump line describes natural rubber as the standard compound, with neoprene, Buna-N and Viton offered as replacements. Treat that as a guide, not a specification. We do not publish wear or chemical ratings for these compounds because CH&E does not publish them. Tell us what you pump and how hard the pump works, and we will help you choose.

Which pumps this diaphragm fits

The CH&E manual lists P2726 for these 3 inch gas engine powered pumps:

• CH&E 5500 series, aluminum
• CH&E 6500 series, cast iron

The manual uses the same number for both. They differ in the metal used for the wetted parts, not in the diaphragm. Model numbers across this line run from 5500 to 6535.

CH&E built other 3 inch diaphragm pumps outside these series. We have not confirmed this part for those. If your model number does not start with 55 or 65, contact us before ordering.

Magnum and Mud Hog 3 inch pumps are related to this line. A Magnum Products manual for models MCP5537 and MCP6537 uses the same 5500 to 6500 parts drawings. We have not confirmed the diaphragm line item in that manual, so we do not list those pumps as verified. Send us your model and serial number and we will check.

Fitting the diaphragm

The CH&E manual gives these steps for 3 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 holding 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 45 to 54 N-m, which is 35 to 40 lb-ft. Center the diaphragm over the water box. Clamp it with the four bolts in a crossing pattern at the same torque.

The 3 inch torque is higher than the 2 inch figure. Check which pump you have before you reach for a wrench setting from memory.

Parts to check while the pump is open

• Flap valve assembly. CH&E does not list a rubber flap valve for this pump. The 3 inch options are Buna-N SA-10001B, neoprene SA-10001N, Viton SA-10001V, and SA10002N which is neoprene with a cloth insert. The parts list shows SA-10001N as standard fitment. Note these are a different series from the 2 inch flap valves
• Diaphragm bottom plate, P3306
• Retaining washers, P3317, two per pump
• Connecting rod, P3305

If more than one is worn, the rubber rebuild kit W103-030.0R may cost less than buying parts one at a time.

Need help identifying your part

Send us your pump model number, your serial number, any number stamped on the old diaphragm, and a measurement across its widest point. Ken’s Distributing will match it against the CH&E parts list and tell you what you need.

Frequently Asked Questions

What pumps does part number P2726 fit?

P2726 is the diaphragm listed in the CH&E parts manual for 3 inch gas engine powered pumps in the 5500 aluminum series and the 6500 cast iron series. One number covers both builds, and the model range runs from 5500 to 6535. CH&E also built 3 inch pumps outside these series, and we have not confirmed this part for those. Check your nameplate first. If your model does not begin with 55 or 65, contact us before ordering.

My old diaphragm has no number stamped on it. How do Iidentify it?

Measure it and photograph it. Take the width across the widest point, then the thickness, then count the holes and note where they sit. Photograph both faces flat. Send those to us along with the model number and serial number from your pump nameplate. We will match it against the CH&E parts list. Do not order by appearance alone, because diaphragms from different pumps can look almost identical and still mount differently.

Is the 3 inch diaphragm the same as the 2 inch one?

No. They are different parts with different numbers. The 3″ diaphragm for the 5500 and 6500 series is P2726. The 2 inch diaphragm for the 5400 and 6400 series is P2331. They also use different torque settings and different flap valve assemblies. The 3 inch is physically larger. If you run both sizes on your crew, label your spares, because mixing them up is one of the most common ordering mistakes we see.

My pump model does not start with 55 or 65. Will this fit?

We cannot say without checking. The CH&E manual we work from covers the 5500 and 6500 series only. CH&E built other 3 inch diaphragm pumps under different model numbers, and we have not verified which diaphragm those take. Send us your full model number and serial number from the pump nameplate. If you can, add a measurement across the widest point of your old diaphragm. We will confirm it before you spend anything.

What does the R mean in P2726R?

The letter at the end shows the compound. R means rubber. CH&E uses one base number with a different letter for each material. You will see N for neoprene, B for Buna-N, V for Viton and TPE for the TPE version. Older paperwork may show P2726 with no letter at all. Every version shares the same shape and mounting, so the letter tells you the compound and nothing else.

Which flap valve goes with a rubber diaphragm on a 3 inch pump?

CH&E does not list a rubber flap valve, so it will not match your diaphragm compound. The 3 inch options are SA-10001B in Buna-N, SA-10001N in neoprene, SA-10001V in Viton, and SA-10002N which is neoprene with a cloth insert. The parts list shows SA-10001N as standard fitment. These numbers are different from the 2 inch flap valves, so check your pump size before ordering one.

What torque should I use when I fit this diaphragm?

The CH&E manual gives 45 to 54 N-m for 3 inch pumps, which is 35 to 40 lb-ft. Use it twice. First on the three nuts holding the diaphragm to the diaphragm bottom plate. Then on the four bolts clamping the diaphragm between the pump frame and the water box. Tighten those four in a crossing pattern so the clamp is even. The 2 inch figure is lower, so check your pump size first.

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

Check the flap valve assembly first, since there is no rubber version and yours may be a different compound. Then look at the diaphragm bottom plate P3306, the two retaining washers P3317, and the connecting rod P3305. These sit next to the diaphragm and wear at a similar rate. If more than one is worn, the rubber rebuild kit W103-030.0R may cost less than single parts. Ask us and we will tell you which suits your pump.