What the maker puts in writing
- “Our Regal water closet diaphragm assembly kit is intended to replace worn or end of service life assemblies. The diaphragm is built with proprietary natural rubber with a brass bypass. This kit includes the diaphragm, handle repair kit, vacuum breaker repair kit and tailpiece O-Ring”
- “This water closet diaphragm assembly is specifically designed to work as a replacement for our line of Regal 3.5 GPF flushometers (Clamshell # 33170011). Always make sure to check part compatibility”
- “Worn-out diaphragms can lead to water waste or incorrect flushing amounts”
- “KIT COMPONENTS INCLUDED: Includes A-38-A Diaphragm, Handle Repair Kit, V-551-A Vacuum Breaker Kit, and Tailpiece O-Ring”
- “DUAL PART NUMBER LISTING: This product is available under two part numbers: 3317003 and 33170011. Both are the exact same item with identical specifications”
First: this is not a household part
A flushometer is the exposed chrome valve on a pipe above a commercial toilet — no tank, no tank, no lid.
It takes water directly from the main water supply and meters out one measured flush. That is why a commercial washroom can be flushed repeatedly with no refill wait, and it requires a large supply pipe and genuine flow — which a house generally does not have.
So this and the Zurn are the two commercial parts on this shelf, and they are not alternatives to the seven tank parts beside them. If your toilet has a tank with a lid, none of this applies.
Every part named
A-38-A Diaphragm. Handle Repair Kit. V-551-A Vacuum Breaker Kit. Tailpiece O-Ring.
That is the only itemized kit on this shelf. The Kohler listing, by contrast, calls itself a “canister valve replacement/repair kit” and lists nothing.
For somebody who has to decide whether a box contains what the job needs, that difference is the whole page.
And the vacuum breaker is the part that matters
Here is why it belongs in a diaphragm rebuild.
A flushometer joins supply water to a fixture with nothing in between. If water pressure were to drop, water could in principle be drawn back out of the fixture into the supply.
A vacuum breaker admits air and breaks that siphon. It is a safety device, not a convenience.
Renewing the diaphragm and leaving a fifteen-year-old vacuum breaker in place is an unfinished job — and this kit includes a new one.
No other listing on this shelf mentions backflow prevention, because a tank toilet does not need it: the tank is the air gap.
The two part numbers
3317003 and 33170011. Both are the exact same item… if you have been sourcing either part number, this listing covers both.
In a facilities store that is a real saving. A part listed under two numbers generates duplicate stock, failed orders and arguments with suppliers.
A sentence like that only gets written by somebody who has taken the phone calls.
One material note
The diaphragm is proprietary natural rubber with a brass bypass.
Worth reading beside the Zurn on this shelf, which publishes chloramine-resistant seals for the same kind of duty and makes a point of it. Chloramine is what municipal water increasingly uses in place of free chlorine, and it is harder on rubber.
“Proprietary” may well mean a compound formulated for it. The listing does not say, and Zurn does.
And the limit to check first
Regal line. 3.5 GPF. Manual.
A Regal flushometer set for 1.6 or 1.28 gallons needs a different diaphragm, and a sensor-operated valve is a different animal entirely.
Always make sure to check part compatibility — which, on a shelf where several listings publish an exclusion, is the standing advice for all of them.
Availability
Available at around $28.99 on Amazon.com when we checked on October 29, 2026, for delivery to a US address.
Stock and prices on Amazon.com move without notice; the button above opens the live listing.
Prices quoted in this text were read on October 29, 2026. The live price is at the top of the page.
