Sloan Automatic Flush Valve Troubleshooting (9 Issues Fixed)

Wouldn’t it be great if you could avoid having to use your hands to flush the toilet, especially in public? Well, automatic flush toilets could be a great addition to your home, and the best part is you can repair them should they malfunction. Sloan automatic flush valve troubleshooting guide addresses common issues.

Some of the issues you should know how to address include wrong flush length, chattering noise, continuous running, inconsistent flush, and insufficient water. Also, the flush valve can leak, splash water, or stop flushing.

With the proper guidance, you can troubleshoot and fix these problems. This post provides a step-by-by-step guide for troubleshooting and solving Sloan automatic flush valve problems.

Sloan automatic flush valve blinking red

Sloan Automatic Flush Valve Problems (Quick Fix)

 ProblemPossible CauseRecommended Fix
1.Flush length too longClogged bypass orifice in the diaphragm
Damaged relief valve and inside cover
Low water pressure
Remove the clog Replace the diaphragm
2.Flush length too shortA worn-out or damaged diaphragm assembly
A mismatch between the diaphragm assembly and the fixture
Replace the diaphragm assembly
Install the diaphragm assembly that is compatible with the fixture
3.Inconsistent flushFluctuation of pressureCheck the system’s pressure
4.Chattering noiseDegraded piston lip seal
Faulty relief valve
Replace the defective piston assembly and the relief valve

1. Flush Length Too Long

A clogged bypass orifice in the toilet diaphragm can prolong a flush. Foreign materials or a sticky film from treated water could cause clogging.

An improperly installed or damaged relief valve or inside cover will make your toilet flush longer than usual. Additionally, you will confront protracted flushing when you place a water-saver diaphragm mechanism in a unit that uses little water.

The relief valve seat demands high water pressure to seat, meaning low water pressure will do the opposite and would contribute to unsatisfactory long flushes. In troubleshooting this, professionals caution against enlarging or damaging the relief valve since that will only create more problems.


  • Take out the diaphragm assembly.
  • Separate the filter rings from the diaphragm.
  • Clean the diaphragm and ensure you remove the clogs.
  • Consider replacing the diaphragm assembly if the above steps cannot solve the issue.
  • Replace the relief valve and the inside cover if necessary.
  • Check the required volume indicator in the tank so you can install a relief valve or diaphragm assembly that is compatible with the fixture.
  • If the problem stems from low pressure in the water supply line, cut off the control stops to restore the pressure, then open them.

2. Short Flushing

Sometimes, your flushing can last shorter than the recommended time and could spring from a valve turning off immediately after activation. This Sloan automatic flush valve problem has multiple causes.

Just like the “flush length is too long problem,” installing a diaphragm assembly meant for low water consumption units in a conventional fixture will result in short flushing.

A loose guide assembly and a worn-out diaphragm, a damaged or corroded bypass orifice, will make your toilet have short flushes. Also, look out for a faulty handle assembly when troubleshooting these issues.


  • Replace the diaphragm and the handle assembly.
  • Check the level indicators in the fixtures to determine the type of diaphragm assembly to install.
  • Hand-tighten the guide assembly and the diaphragm assembly.
  • Replace the corroded and damaged bypass orifice.

3. Flush Valve Runs Continuously

The Sloan automatic flush valve can run continuously and impact your water bill. However, troubleshooting the problem requires that you know whether your unit is a piston or diaphragm type.

For piston fixtures, factors like a faulty relief valve seat, low water pressure, and debris buildup under the piston and on the bypass orifice can cause the flushometer to run continuously.

As for diaphragm units, you may need to deal with debris blocking the diaphragm bypass and the solenoid sticking open.


  • Replace faulty relief valve seat.
  • Check water supply line pressure.
  • Clean the piston or diaphragm to remove debris.
  • Replace the solenoid mechanism.
  • Replace compromised diaphragm assembly.
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4. Flush Valve Is Not Flushing

As the flush valve serves you day in and day out, a time will come when deterioration will set in and stop it from flushing. Besides wearing down, a loose cover, low pressure, and incorrect piston installation (for piston fixtures) will impede the flush valve’s normal functions.


  • Tighten the cover.
  • Adjust the control stop to raise the water pressure.
  • Install the pistons correctly.
  • Consider replacing worn-out pistons.
  • Install the proper GPF diaphragm.

5. Insufficient Water To Siphon The Fixture

Another setback with the Sloan automatic flush valve is a below-par flush resulting from inadequate water supply and the installation of urinal parts in the closet valve. A lack of water supply reduces water pressure and limits the water needed to flush your fixture.

A closed control stop, fitting a low consumption valve in a high consumption unit, and having a water saver kit in a bowl not designed to save water will also deny your fixture water to siphon.


  • Measure the volume of water and pressure at the valve.
  • Disconnect the relief valve and the diaphragm assembly.
  • Remove the restriction ring and keep the control stop open.
  • Adjust the control stop to allow more water into the system.
  • Install compatible accessories in your fixture to avoid problems caused by a mismatch.
  • To increase the water flow, replace the refill head with a brass low-flow refill head.
  • Replace the urinal parts with the recommended closet valve parts.

6. Sloan Automatic Flush Valve Splashing Water

Two chief causes of water splashing from the valve are incorrect installation of the diaphragm assembly and leaving the control stop wider than what professionals recommend. Apart from that, installing a closet diaphragm mechanism in a urinal and placing a water saver on a low-consumption unit will splash water on your floor, leaving it wet and slippery.


  • Examine the markings on your flush valve to determine the correct volume of water required and compatible accessories to install in your toilet.
  • Replace the closet diaphragm with a urinal diaphragm system.
  • Adjust the control stop to regulate the water getting into the fixture.

7. Automatic Flush Valve Leaking

Water leaking and running continuously comprise flush valve challenges that will see you spend more than you have to meet unprecedented water bills. Sloan automatic flush valves can leak from the tailpiece, handle, control stops, vacuum breaker, spud flange coupling, and flushometer cover.

Leaking persists when the aforementioned components wear out or degrade (like in the case of O-rings). In other instances, loose valve cover and spud coupling also contribute to water leaking from the Sloan automatic flush valve.


  • Cut off the water supply and tighten the flush valve cover.
  • Replace the faulty handle, tailpiece, control stop, and vacuum breaker.
  • Tighten the spud coupling.
  • Avoid over-tightening the vacuum breaker coupling.
  • Replace defective gaskets.
  • Swap the fractured inner valve cover with a new one.
  • Get a new B-39 seal.

8. Inconsistent Flush

When it comes to flushing problems, many homeowners know about toilet flushes being either too long or too short. Nevertheless, the flush valve can exhibit irregular flushing patterns whereby the long, short, and normal flushes alternate.

Fluctuation of pressure within the fixture is the principal cause of such inconsistencies.


Check the pressure in the plumbing system and make necessary adjustments.

9. Chattering Noise In Automatic Flush Valve At Shut Off

It wraps up the problems associated with the Sloan automatic flush valve. How you diagnose the problem depends on whether your flush valve is piston- or diaphragm-operated.

Piston valves will confront you with loose plumbing, degraded piston lip seal, and high flow pressure. Chattering noise from diaphragm valves can arise from a faulty inside cover, relief valve, or the diaphragm assembly installed upside down.


  • Tighten the plumbing.
  • Install the diaphragm according to the labels on it.
  • Adjust the control stops to reduce flow pressure.
  • Check for faulty inside covers, relief valves, and diaphragm assemblies and replace them if needed.
  • Replace the defective piston assembly.
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How Often Should You Replace Control Stops?

The lifespan of control stops depends on their usage, water quality, pressure, and main breaks. Prevalent weather will also determine the longevity of these flush valve components.

Although it is difficult to predict how long control stops will last, symptoms such as the valve running continuously and control stops not closing (and opening) suffice to warrant replacement.

How To Adjust A Control Stop

  • Detach the cap from the control stop using a flat screwdriver.
  • Thread the screwdriver blade between the body of the control stop (the flat surface) and the cap’s bottom edge.
  • Lift the cap gently.
  • Rotate the screwdriver around the cap until you can hold it and take it off the sleeve.
  • Ensure the sleeve remains connected to the control stop’s bonnet.

Final Thoughts On Sloan Automatic Flush Valve Troubleshooting

Sloan automatic flush valves have garnered worldwide popularity because of their efficient functionalities. However, they aren’t flawless since they have problems like leaking, splashing water, chattering noise during shut-off, and many more.

Thankfully, this post details the main concerns with these fixtures and how to fix them.

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