HydroLogic Hydroid Carbon Pre-Filter, 75,000 Gallon Replacement (HL 11591)

Hydroid Carbon Pre-Filter: First Stage of the Hydroid RO

This cartridge is the first stage of the HydroLogic Hydroid compact commercial reverse osmosis system. HydroLogic lists it as part number HL 11591, and each Hydroid runs one. It is an encapsulated hybrid filter, combining sediment capture and carbon treatment in a single sealed cartridge. Feed water passes through it before reaching the pump and the two RO membranes downstream. The Hydroid membranes have a chlorine tolerance of 0 ppm, so the carbon stage carries real weight. Chlorine that slips past it damages the membrane material, and oxidation damage is not covered under warranty. The sediment side keeps silt and particles from loading up the membrane surface. HydroLogic rates the cartridge for 75,000 gallons of purified water. Heavy sediment in the feed water shortens that life, so a sediment-rich source may call for earlier changes. The Hydroid manual also gives a pressure test for replacement timing. Swap the filter when the feed gauge drops 15 psi or more below its startup reading. A system that logged 60 psi at startup, for example, needs a new cartridge at 45 psi.

Installing a HydroLogic Replacement Filter

Turn the system off, shut the feed water, bleed off all pressure and unplug the unit first. Every gauge should read zero before any housing is opened. Pull the red locking clip, press the grey collet and slide the tube free. Remove the two locking crescents with a #5 hex wrench, then pull the end plug with the removal tool. Lift out the old cartridge, which may take long-nose pliers and a gentle rocking motion. Coat the new seal and O-rings with the silicone packet that comes with the filter. Petroleum-based lubricant should never touch these parts. Note the flow arrows on the housing and seat the filter fully against the bottom end plug. Push the end plug back evenly, refit the crescents and tighten them snugly. Before reconnecting the system, flush carbon dust out through the black flush tubing. Run water until the stream clears, which takes about five minutes. Keep that black tubing for the next change, then log the new feed pressure as your baseline.

Key Features

• Hybrid sediment and carbon stage: Removes silt and chlorine in one encapsulated cartridge.
• 75,000-gallon rating: HydroLogic's change interval for purified water produced.
• Membrane protection: Shields the 0 ppm chlorine-tolerant Hydroid membranes.
• Pressure-based timing: Change at a 15 psi feed-gauge drop from the startup reading.
• OEM part HL 11591: The carbon filter specified in the Hydroid manual.

Technical Specifications