Question 1

i installed it but when i flip the switch to filtered, no water comes out at all. unfiltered works fine.

Accepted Answer

DIAGNOSIS This points to a complete blockage in the filter path. Either the new filter cartridge has a manufacturing defect (rare), or, more likely, the protective cap wasn't removed from the end of the filter. FIX Turn off the water and unscrew the housing. Remove the filter cartridge. On the top end (the nipple that sticks up), there should be a clear or blue plastic cap. You need to peel or pry this cap off—it's a shipping seal to keep the filter media sterile. Once removed, reinstall the cartridge and housing. IF THAT DIDN'T WORK The internal diverter valve in the head might be stuck in the "bypass" position. Try flipping the switch back and forth firmly several times with the water on low. Sometimes it can get hung up. If that fails, the valve mechanism itself may be faulty. HEADS UP Always check both ends of a new filter. Some older models also had a rubber tip on the bottom to pull off. Modern PFM400C cartridges usually just have the one top cap. If water never flows, don't force the switch—you could damage the lever.

Question 2

the electronic indicator light never comes on at all, not red or green, is the battery dead?

Accepted Answer

DIAGNOSIS Almost certainly. The light is powered by a single 4LR44 (or equivalent) 6-volt alkaline battery housed in a compartment on the bottom of the filter head. FIX Unscrew the filter head from the faucet. On the underside, you'll see a small rectangular battery cover. Use a coin to turn the screw and open the cover. Replace the old battery with a new 4LR44 6V battery, ensuring the positive (+) terminal faces the compartment's center (usually marked). Close the cover tightly. IF THAT DIDN'T WORK Check for corrosion on the battery contacts. If you see white or blue crust, clean it off gently with a cotton swab and a bit of vinegar or rubbing alcohol. Also, ensure the new battery is fresh and seated correctly. HEADS UP The filter will still work perfectly without the light—it just becomes a manual-change system. The battery typically lasts through 2-3 filter changes (about a year). A dead battery doesn't affect filtration performance.

Question 3

water is coming out around the switch lever on the side, not from the spout, is it broken?

Accepted Answer

DIAGNOSIS The internal diverter valve seals are failing. This is a wear-and-tear part that directs water either through the filter or around it (for unfiltered). When the seals go, water leaks out the side. FIX For the PFM400H, the fix is usually replacing the entire filter head unit. The internal valve isn't designed to be user-serviceable. Contact PUR customer support. They often send a replacement head under warranty if it's within 1-2 years of purchase. IF THAT DIDN'T WORK Before you conclude it's the valve, make sure the leak isn't actually coming from a higher point and just running down. Dry everything thoroughly, then run water while watching closely. If it's truly seeping from the seam around the plastic switch lever, it's the diverter. HEADS UP Using hot water with this filter can accelerate the wear on these plastic internal parts. The PUR faucet filter is only rated for cold water use. Running hot water through it can warp seals and cause this exact leak.

Question 4

the filter head won't screw back onto my faucet after i took it off to clean, the threads won't catch.

Accepted Answer

DIAGNOSIS The plastic adapter that stays on your faucet has likely become cross-threaded or has a piece of debris stuck in the threads. FIX First, unscrew the entire adapter from your faucet spout. Inspect the plastic threads on both the adapter and the filter head. Look for any plastic shavings, sand, or scale buildup. Clean them with an old toothbrush. Now, re-thread the adapter onto your faucet by hand, going *slowly* and counter-clockwise first until you feel the threads drop into place, then tighten clockwise. Then try attaching the filter head. IF THAT DIDN'T WORK The plastic threads on either the adapter or the filter head might be stripped. Compare them visually. If they look worn or flattened, that part needs replacing. You can order a new faucet adapter kit from PUR. HEADS UP Never force it. The plastic used is durable but can strip if you muscle it. Always start threading by hand and never use pliers on the plastic housing—only on the metal collar of the faucet adapter if you must.

Question 5

my filter makes a loud rattling or vibrating noise when i turn the water on, sounds like it's gonna explode.

Accepted Answer

DIAGNOSIS That's usually trapped air in the system. When you change the filter, an air pocket can get locked in the housing, and water rushing through causes it to vibrate noisily against the plastic. FIX Purge the air. Turn the filter to the "on" (filtered) position. Slowly turn on the cold water at the faucet to a medium flow. Let it run for a full 2-3 minutes. You should hear the sputtering and rattling decrease and then stop as the air is forced out. It might take a bit for the flow to steady completely. IF THAT DIDN'T WORK Check that the filter cartridge is seated correctly and fully pushed down into the housing. A crooked or partially inserted cartridge can cause turbulent water flow. Also, ensure the housing is screwed on tightly and evenly—cross-threading can cause weird flow issues. HEADS UP This is normal after a filter change and isn't harmful, but if the noise *starts* suddenly on an old filter, it could be a sign the internal components of the cartridge are breaking down. Time for a replacement.

Question 6

water pressure from my PUR faucet filter is super weak, just a dribble, is the filter already clogged?

Accepted Answer

DIAGNOSIS Most likely, yeah. A sudden, severe drop in flow means the filter cartridge is saturated with sediment and needs replacing, even if the light isn't red yet. FIX Swap the filter. Unscrew the housing, remove the old PFM400C cartridge, and drop in a new one. Before you install the new one, quickly run water through the *empty* housing for a second to flush out any loose debris that settled in the bottom. Reassemble and check the flow. IF THAT DIDN'T WORK The problem might be upstream. Unscrew the filter unit entirely and check the flow directly from your faucet's aerator (the little screen on the end). If it's also a dribble, your main faucet aerator is clogged with scale. Clean or replace that separately. HEADS UP If you have well water or very high sediment, you might go through filters faster than the 100-gallon/3-month guideline. Consider adding a pre-filter at your main line if this happens constantly.

Question 7

the filter light on my PFM400H just stays red all the time even though i just put a new filter in, how do i reset it?

Accepted Answer

DIAGNOSIS Yeah, this one's common. The electronic filter indicator didn't reset when you installed the new cartridge. It's a separate step people often miss. FIX With the filter installed and the unit mounted on the faucet, find the small circular "Reset" button on the front of the housing, near the light. Press and hold that button for about 3 seconds. You'll see the light cycle from red, to blinking yellow/amber, and then settle on solid green. That means it's reset for a new filter's lifespan. IF THAT DIDN'T WORK Make absolutely sure you're using a PUR PLUS faucet filter (like the PFM400C), not a standard PUR filter without the "Plus" technology. The non-Plus filters aren't compatible and won't trigger the sensor properly. Also, check that the battery cover on the bottom is securely closed. HEADS UP The indicator is just a timer based on average gallon use. If your water is particularly hard or has high sediment, the filter might clog *before* the light turns red. Don't rely on the light alone if water flow slows to a trickle.

Question 8

my new PUR PLUS faucet filter is leaking water from the top where it connects to the faucet, i tightened it as much as i could.

Accepted Answer

DIAGNOSIS This is almost always a gasket or o-ring issue, not a tightening problem. The included rubber gasket is either missing, installed incorrectly, or got pinched during setup. FIX First, turn off the water and unscrew the filter unit from the faucet adapter. Check the black rubber gasket inside the adapter's threaded collar. Make sure it's seated flat in its groove, not twisted or folded. If it looks good, reinstall it and hand-tighten the unit—don't use tools or extreme force. Turn the water back on slowly. IF THAT DIDN'T WORK The gasket might be defective or the wrong size. PUR includes a spare gasket in the box. Swap it in. If you lost it, you can order a replacement gasket kit (often part #RFGPK) directly from PUR. HEADS UP Overtightening can actually warp the plastic adapter or damage the gasket, causing the leak you're trying to stop. It only needs to be snug enough to stop drips when the water is off.

PUR PLUS Faucet Mount Water Filter PFM400H

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