A "Green" Company Since 1990

HydroCell "High Rate" Series Sand Filters

HydroFlo High Rate Automatic Backwashing Sand Media Filters are designed for general-purpose water filtration. These permanent media, automatic backwashing filters will remove organic and/or inorganic suspended solids down to 20 microns in size. Through the use of automatically controlled backwashing, the filter will operate “on line” for extended periods of time prior to the short backwashing cycle. Automatic filter operation is monitored on elapsed time, as well as pressure differential. When the controller “calls” for a backwash as a result of pressure differential or elapsed time, the backwashing function utilizes a portion of the clean filtered water produced by the system to clean the media. Single tank systems utilize unfiltered water for backwashing. Optional external backwash water sourcing systems are available for both single and multiple tank systems.

The standard HydroFlo single media sand filter utilizes a vertical side shell depth of 24”. Deep bed sand media filters featuring a 36” deep side shell are also available. HydroFlo sand media filters feature catalyzed epoxy linings, cast iron automatic valves, solid state automatic controls and type 304 stainless steel underdrains. Standard HydroFlo systems are shipped assembled on structural steel skids for easy installation and start-up. Standard inlet and outlet connections are flanged, but may be ordered grooved as an option.

HydroFlo in-line sand media filters are ideally suited for use in water re-use applications, water pre-treatment applications (for reverse osmosis and deionization systems, etc.) or as a pre-treatment prior to disposal bag or cartridge filters. In-line sand media filters are also widely used as primary filters for removal of suspended solids in incoming plant water or in wastewater clean up applications. Air scour and surface wash options are available if required.

Standard Features

  • Skid Mounted

  • Pre-piped
  • Pre-wired
  • State of the art NEMA-4X, UL 508 electrical enclosure
  • Compact design for small footprint
  • TEFC mixer motor
  • Factory tested
  • Stand alone operation
  • Seamlessly integrates with other HydroFlo wastewater products

Available Options

  • Available in epoxy coated carbon steel, Stainless steel, polypropylene, FRP, exotic alloys and all thermoplastics for long life and superior corrosion resistance

  • Influent equalization
  • Influent / effluent lift stations
  • On board reagent storage (day tanks)
  • Ultrasonic level control
  • Duplex systems for redundancy
  • Effluent pump
  • SCADA system monitoring
  • Final effluent Monitoring
  • Final effluent sampling
  • Explosion-proof design
Equipment Design Data & Sizing Calculations

Application Questionnaire


General Arrangement


• Standard Engineering

"Common" Engineering
  Applicable to all HydroFlo
  Manufactured Equipment

Installation, Operation & Maintenance Manuals

Standard IO&M Manual

General IO&M
  Applicable to all HydroFlo
  Manufactured Equipment

Equipment Criteria

The HydroFlo Tech HydroCell High Rate,Three-Cell Pressure Sand Filter system is an automatic, reliable and economical way to remove suspended solids from water and wastewater. The HydroCell High Rate Pressure Sand Filter system is designed as a three cell, parallel flow filter with pressure differential sensing, automatic backwash. The HydroCell performs backwashes of the three individual filter media beds sequentially, one at a time, using same source filtered flow from the other two vessels, or optionally, using separate source backwash. The HydroCell design permits the filtration system to continue filtering during backwash cycles

The Equipment

The basic system is comprised of a skid, pressure vessels, valves, plumbing, and a control panel.


A steel skid is provided for supporting the entire system. The skid features a welded 4" steel "C" channel frame, and a 1/4" steel deck plate. The skid is provided with anchor attachment points suitable to satisfy UBC seismic zone 4. The entire skid is blasted to an SSPC-SP6, and coated with a 2 part self priming epoxy finish for corrosion resistance. The skid color is OSHA Safety Blue, unless otherwise specified.

Optional Containment Pan: As an option, a containment / drip pan can be provided for protecting the steel skid from leaking or spilled corrosive fluids. A drain connection is provided for plumbing the containment pan to a suitable location. The pan can be fabricated from polypropylene, stainless steel, etc. and features 8" high walls.

Filter Piping Manifold:

The manifold is fully assembled, wet tested and installed. The manifold is properly supported with a steel frame support system designed to withstand typical transportation and installation stress and provide a stable operating configuration.

Filter Distribution Manifold:

The vessel influent and effluent distributor manifolds are provided as a matched set, designed for minimum pressure loss at design and backwash flow rates. The influent diffuser hub is provided with sufficient openings, of sufficient size, to allow solids laden influent and solids laded backwash to easily pass. The effluent diffuser hub and radial arranged slotted laterals are designed with sufficient surface openings to properly retain filtration media. The number of slots and the slot width is appropriately selected to ensure proper performance based on filtration conditions and media selection.

Automatic Flow Control Valves:

The control valves provide flow diversion and facilitate the sequential backwash operations. The valves are pneumatically operated and are actuated with air tubing routed from the actuation solenoid valves. The valves are true union type, double shaft seal diaphragm valves. The pneumatic valves are provided with a removable cap seal design, permitting valve disassembly and repair without tools or without removal from the piping. The valves are provided with electric actuated air control 3 way solenoid valves with vent outlet. The pneumatic control valves are provided in a limit stop flow control configuration. The valves can be optionally electrically operated with motor actuators.

Filtration Vessels:

The three filtration vessels are provided as vertical cylindrical vessels with top entry influent distribution header and bottom exit effluent manifold with radial headers from a center mounted hub. The filter vessels are rated for > 100 psi working pressure with flanged connections and suitable heavy duty support bases. The vessels shall provide a hydraulic loading ratio of between 5 and 9 gpm/ sq.ft. of bed surface area. The vessels are pre-plumbed in parallel.

Media (single media):

The filter is provided with a single filtration media with support bed media. All filter media shall conform to the requirements of AWWA B100. Sieve analysis shall be performed in accordance with ASTM C 136 and AWWA B100. Specific gravity shall be determined in accordance with ASTM C 127 for support media and ASTM C 128 for high density media. The medias shall be free from impurities of any kind including shale, mica, clay, loam, or organics.

SILICA SAND (filtration media) (minimum depth = 2”) The silica sand shall have an effective size between 0.40 mm and 0.55mm, uniformity coeffecient less than or equal to 1.6 and a specific gravity of 2.55. Ninety five percent shall be larger than or equal to 0.50mm.

GRAVEL (support media) (minimum depth = 4” above effluent header)
The support media shall be a gravel or quartz consisting of 0.3 mm to 0.6 mm, hard, rounded stones with an average specific gravity of not less than 2.65. Not more than 5 percent by weight shall have a specific gravity of 2.6 or less. The gravel shall contain not more than 5 percent by weight of thin, flat, or elongated pieces (elongated pieces are those that in the largest dimension exceeds three times the smallest dimension).


The filter is provided with a differential pressure sensor that is pre-installed in the piping manifold. The sensor is a single set point type that can be field adjusted. The sensor is provided in NEMA 4 configuration.

Control Package:

All HydroFlo Tech HydroCell Deep Bed, Three-Cell Pressure Sand Filter systems are fully automated. Control packages (depending on your specific requirements) are available in either basic relay logic controls, or a full state of the art PLC with touch screen HMI and our sophisticated treatment algorithms. The relay logic controls package allows basic reconfiguration of the original system settings, while the PLC based package allows maximum flexibility to change the process parameters, as well as tight control that minimizes chemical usage. We can include a variety of options including digital data logging of critical process parameters, ethernet access to process data, communication with Building Management Systems, and even remote system access using cellular wireless technology.

All enclosures are NEMA 4X. Where metallic enclosures are used, they are provided with epoxy or polyester finishes for corrosion resistance. All conduit is plastic coated, where possible. Low voltage 24VDC is used throughout to minimize service personnel exposure to high voltage. All panels are OSHA LOTO and NFPA 79 compliant. UL-508 listing is available.

Effluent Monitoring: As mandated by the local controlling authority, the effluent quality must be continuously monitored. A two pen recorder is to be used to monitor effluent flow rate and pH. The recorder is to be equipped with a flow totalizer. Any effluent pH deviations will trigger an alarm and system discharge will be halted.

System Packaging:

The system is supplied as a completely fabricated "turnkey" package. All devices are pre-wired and plumbed.

You need to make the plumbing connections to and from the system and a single electrical connection point for incoming power. The disconnect on the MCP provides OSHA Lock Out / Tag Out and NFPA 79 compliance. For systems requiring compressed air, only one connection is required and the valve is supplied for OSHA LOTO.