Sloan Royal Flushometer Rebuild Procedure

Why this matters

The Sloan Royal series is the workhorse manual flushometer on commercial water closets and urinals across North America (Royal 110 series for closets, Royal 180/186 for urinals). When a Royal fails open and runs continuously or fails closed and refuses to flush, the building owner is paying for water at the meter while staff and tenants escalate complaints. A full diaphragm-relief-valve rebuild restores OEM performance in under 20 minutes per fixture if done in sequence; misidentifying the kit or the diaphragm gpf rating sends the tech back to the supply house mid-job.

Identify the model and the kit

The Royal model number is stamped on the chrome cover or printed on the relief stem cap:

• Royal 111: 1.6 gpf water closet (most common modern)
• Royal 110: 3.5 gpf water closet (pre-1992 buildings)
• Royal 113: 1.28 gpf high-efficiency water closet
• Royal 152: 1.0 gpf low-flow water closet
• Royal 180: 1.0 gpf urinal
• Royal 186: 0.5 gpf high-efficiency urinal
• Royal 195: 0.125 gpf pint urinal

The rebuild kit must match the gpf rating. The diaphragm is color-coded and marked with the gpf value on the diaphragm itself. The Sloan A-1102-A kit fits the Royal 111 (1.6 gpf); A-1107-A fits the Royal 113 (1.28). Do not interchange. A 1.6 gpf diaphragm in a 1.28 gpf valve over-flushes; the reverse under-flushes and the bowl does not clear.

Pre-shutoff verification

Before turning off the control stop:

1. Test the flush. Note whether the valve fails by running continuously, by short flushing (less than full volume), by failing to start, or by sticking partially open after flush.
2. Inspect the bowl outlet for evidence of debris or vandalism (objects in the trapway will mimic flushometer failure).
3. Look at the relief stem position when at rest. A stem that is depressed below the cover face indicates a failed relief valve or a contaminated upper chamber.
4. Verify the control stop turns. A stop that is frozen open requires a separate replacement procedure not covered here.

Shutoff and disassembly

1. Close the control stop using the screwdriver slot on top of the stop. Some older Royal valves use a Sloan-key on the control stop instead; bring the key.
2. Flush the valve once to drop residual pressure in the upper chamber.
3. Use a Sloan spud wrench (or a smooth-jawed 14 inch slip joint plier with a leather strip wrapped around the cover) to unthread the outer chrome cover. Turn counterclockwise. Do not use pipe wrench teeth; they mar the cover and the building owner notices.
4. Lift off the cover. The inner cover (upper chamber housing) is also threaded; remove with the same wrench.
5. Lift out the diaphragm assembly. The current Sloan part is a single-piece kit with diaphragm, relief valve, refill ring, and guide assembly pre-assembled.
6. Inspect the seat (the brass machined ring inside the body that the diaphragm seals against). The seat must be smooth and free of mineral deposits. If pitted, replace the seat using Sloan kit A-37 (seat repair). If badly corroded, valve body replacement is required.

Install the new diaphragm

1. Wipe the seat clean with a non-abrasive pad. Do not use sandpaper on the seat; it will leak forever after.
2. Press the new diaphragm assembly into the body, ensuring the bypass orifice in the diaphragm is on the side closest to the spud (toward the bowl). The bypass orifice is the tiny hole in the diaphragm that meters the upper chamber refill; if installed backwards the valve will not seat.
3. Thread the inner cover on by hand, then snug with the spud wrench. Sloan specifies hand tight plus 1/8 turn. Over-tightening cracks the cover.
4. Thread the outer chrome cover on, hand tight plus 1/8 turn.
5. Open the control stop slowly. The valve should fill silently. If you hear a hiss, close the stop and re-check seating of the diaphragm.

Adjust the control stop

The control stop is the volume adjustment, not an on/off shutoff in normal use. Adjust per the gpf rating:

1. Open the control stop fully (counterclockwise).
2. Flush once and observe.
3. Close the stop gradually clockwise until the bowl just barely siphons fully and the trap re-seals at the end of the flush.
4. Make a quarter turn open from the just-barely-flushes position. This is the working adjustment.

A control stop opened too far wastes water and creates back-pressure shocks on the water main. A stop closed too far leaves the bowl unflushed and the trap unsealed (sewer gas).

Failure modes after rebuild

If the valve runs continuously after rebuild:

• Diaphragm installed upside down (bypass orifice on wrong side)
• Debris on the seat under the new diaphragm
• Relief valve held open by contamination from the upper chamber
• Inner cover not seated; upper chamber bleeds to atmosphere

If the valve will not flush after rebuild:

• Control stop closed too far
• Handle assembly worn (separate H-553-A kit)
• Bypass orifice in the diaphragm clogged with construction debris (flush the supply line for 60 seconds with diaphragm removed)

References

• Sloan Royal Flushometer Installation, Operation, and Maintenance Instructions (Sloan document 0816371, current revision)
• ASSE Standard 1037-2015 Performance Requirements for Pressurized Flushing Devices for Plumbing Fixtures
• ASME A112.19.5 / CSA B45.15 Trim for Water Closet Bowls, Tanks, and Urinals
• International Plumbing Code (IPC) 2024, Section 425 Flushometer Valves and Tanks