Accessories & Parts

3300 Altitude Pilot

The 3300 senses tank head (pressure) under its diaphragm and balances it against an adjustable spring load (high level shut-off setting). When tank head is below the setting, the internal mechanism shifts to route the pressure on the main valve diaphragm chamber to atmosphere (bonnet port > vent port), allowing the main valve to open and fill the tank. When the tank head reaches the high level setting, the mechanism shifts to route valve inlet pressure (supply port) to the main valve diaphragm chamber (bonnet port), closing the valve tightly.

On 8” and smaller altitude valves, the pilot operates the main valve as described above. On 10” and larger valves, the pilot operates the main valve through a 3-way auxiliary control, Model 3600.

Typical use: Series 3331 and 3333 altitude valves.

  • Three port, two position, hydraulically operated
  • Extra-large diaphragm, responsive to small level changes
  • Multiple spring ranges for easy, accurate adjustment
  • All parts replaceable while mounted on valve
  • Rubber to metal seat
  • Bronze body, stainless steel internals


  1. Adjusting Screw
  2. Spring
  3. Upper Diaphragm Chamber
  4. Lower Diaphragm Chamber
  5. Pilot Valve Body
  6. To Bonnet
  7. To Supply
  8. To Atmosphere
  9. Tank Pressure Sense Line



Sense line port    –    3/8” NPT
Bonnet port    –    1/2” NPT
Supply port    –    3/8” NPT
Vent/Atmosphere port    –    3/8” NPT
  1. It is essential that the sense line be connected as close to the tank as possible to accurately sense the tank head.
  2. Minimum recommended size for the sense line is 1/2” OD tubing or 3/8” pipe.
  3. In order to prevent air accumulation, the sense line should slope slightly upward from the valve to the tank.





  • Body: Bronze
  • Internal Mechanism: Stainless Steel
  • Elastomers (diaphragm, seat disc, o-rings): Buna-N



Rubber components are typically the only parts that may require periodic replacement. These are available in kits consisting of the diaphragm, the seat disc and all O-rings.
Buna-N Kit    –    Part # 930004


The Model 3300 is shown on OCV Valve Schematics as: 3300symbol

EXAMPLE: Shown here on a MODEL 3331 8” and smaller Altitude Valves.