my pur faucet filter light is solid red and the water stream is really slow, just installed a new filter too.

Diagnosis

The solid red light on your PUR PFM400H indicates a "Filter Replacement Required" status. If you have already installed a new cartridge, the light remains red because the internal timer/sensor does not automatically detect the physical change of the filter; it requires a manual electronic reset to clear the alert. When the light stays red despite a new filter, it often means the reset sequence was either skipped or not held long enough to register. The slow water flow, especially immediately after a replacement, is typically caused by one of two things: trapped air pockets within the carbon block media or an improper seal in the housing. If the filter cartridge isn't seated perfectly flush against the internal gasket, the water bypasses the main flow channel or creates a restriction. Additionally, new PUR filters contain microscopic air bubbles trapped in the filtration media that create "backpressure," which significantly reduces the Gallons Per Minute (GPM) output until the filter is fully saturated.

How to Fix It

To resolve the red light and restore your water pressure, follow these precise steps:

1. Reset the Indicator: Locate the "Reset" button on the top of the faucet head. Press and hold the button firmly for a full 10 to 15 seconds. Do not release it the moment the light changes; hold it until the light flashes green or turns off completely, confirming the timer has been zeroed out.
2. Reseat the Cartridge: Turn off your cold water supply. Rotate the filter housing counter-clockwise to unlock it and remove the new filter. Inspect the O-ring on the filter for any twists or debris. Re-insert the filter, pushing straight up with significant force to ensure it bottoms out. Rotate it clockwise until you feel a definitive "click" and the housing is flush against the faucet body.
3. Purge the Air Lock: Turn your cold water supply back on. Set the faucet to the "Filtered" position. Run the water at full blast for 3 to 5 minutes. You will see "milky" or cloudy water and hear sputtering noises; this is the air escaping the carbon media. Continue until the stream is steady and clear.
4. Verify Flow: Switch the lever back to "Unfiltered" and then back to "Filtered" twice to clear any remaining air pockets from the diverter valve.

If That Didn't Work

• Check for Sediment Blockage: If the flow remains slow, unscrew the filter and look inside the faucet's intake port. Small pebbles or calcium deposits from your pipes can get lodged in the diverter valve during a filter change. Use a toothpick or a small needle to clear any debris from the small holes in the valve.
• Inspect the Gasket Seal: Remove the filter and check the black rubber gasket inside the housing. If it is pinched, cracked, or displaced, it will restrict water flow regardless of how new the filter is. If the gasket is damaged, the housing assembly needs to be replaced.
• Battery Replacement: If the red light refuses to turn off after a 15-second hold, the internal battery (usually a CR2032 or similar depending on the specific PFM400H revision) may be dying. A low battery can cause the logic board to "freeze" the red light status.
• Test the Supply Line: Ensure your shut-off valve under the sink is open 100%. Sometimes, while changing a filter, the valve is bumped or partially closed, restricting the volume of water reaching the faucet.

Heads Up

• Cold Water Only: Never run hot water through the PFM400H filtered setting. Hot water can damage the carbon block structure and cause the filter to leak or lose its effectiveness.
• Avoid Pre-Soaking: Do not soak the filter in water before installation. The filter is designed to be saturated by the actual water pressure of your plumbing system to prevent air locks.
• Replacement Cycle: Replace the filter every 40 gallons or 3 months. Ignoring the red light for too long allows the carbon to become "spent," which can lead to a complete blockage of water flow.
• Avoid Over-Tightening: When locking the filter, stop as soon as you feel the click. Forcing the housing further can crack the plastic threads, leading to permanent leaks.