I have a problem with a 5 Stage Reverse Osmosis Water Filter system (under sink installation).

A hissiing sound at the water dispenser.
I have drained and checked the storage tank air charge pressure (5psi) with what I believe to be an accurate guage. There is no debris blocking the dispenser drain tube where it connects to the sink P-trap.

The dispenser has a small hole (1\4 inch) in the body at the back. I did dislodge something (calcium deposit?) from the waste water outlet and it was fine for 20 minutes.

Hissing sound comes and goes. Still present 24 hours after storage tank has been checked.

Fill sink with water and drain the hissing stops for a while. Shut off water supply at the stop and hissing stops. Open cold water supply and hissing starts again after some random pause.

Eleven months since last filters change.

Can not find explanation as to why one of these systems discharge or waste 2-4 gallons of water for every one useable gallon.

Any troubleshooting suggestions would be apprieciated.

RO systems waste that amount of water due to the way the process works. The RO module allows water to pass through it and does not allow the minerals in the water to pass. Those minerals accumulate in the module and the water needed to send them to the drain is the reason.

I suggest that you change the prefilters in the system.

This hissing sound at the water dispenser is likely from the "air gap" feature in the faucet. I don't know why it should be hissing. Maybe others do.

I'm at a loss on the hissing noise, but I've heard that RO systems work more efficiently at higher pressures because the higher pressures wash the impurities off the membrane better. Mine seems to work better with a larger and finer pre-filter. This removes more of the impurities so the RO doesn't have to work as hard.( Maybe it's just wishful thinking though.)



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Modern RO units are supposed to "turn off" when the tank is full, (earlier ones operated 24/7 and just wasted the unneeded water. You unit may be failing and is not turning off completely.

I talked to manufacturer of system and a customer service Rep gave 3 options to stop the hissing noise at faucet dispenser:
1. Bypass air gap feature in faucet.
2. Check Faucet drain tube from faucet to trap connection for obstructions.
3. Either extend Faucet drain tube and submerge in trap water or use a material like string or fishing line to connect
drain tube at trap entry to the standing
water in the trap.

When I told the customer Rep that it would not be a good idea to bypass the SAFETY feature of the Air Gap, I was told that "homeowners do it all the time". She didn't seem to understand why there is a requirement for the air gap and that bypassing it creates a possible serious health hazzard. Filter or no, I do not want the possibility of sewer water mixed with my drinking water.

The 2nd item I intend to try in a few days and suspect it might be the culprit. I did check the end of the tube where it enters the P-Trap for obstructions but not the entire length of the tube.

I also tried to explain to the customer rep that putting tubes and/or strings into the standing trap water is not a good idea as this could lead to "wicking" the P-Trap dry causing another unhealthy situation (sewer gas through the wicked dry P-Trap.

I am really suprised that this company hasn't been sued from someone getting sick from their advice.

Thanks to all who responed. I'll post the solution when found.

Found Red Tube with small split at faucet dispenser where it slips onto faucet barb.

I don't know why it didn't leak water at the split. But cutting off the split in the tube and reconnection to faucet solved hissing problem.

I have the same hissing problem, but it must be clogged up somewhere along the drain line because i looked at the faucet dispenser drain connection and found no split/leak.
I wonder if one can use a check valve (to prevent health hazard back flow) along the drain line instead of the air-gap?

Had same problem, loud hissing like an air compressor hose coming from air gap on faucet. We lived with it for four months before figuring out the problem. We found it was due to a missing flow reducer. There is a tiny little part that you insert into the 1/4 inch line that runs to the reverse osmosis unit. We placed it in the end of the 1/4 inch line where it connects to the reverse osmosis unit and that did the trick. The problem was that the flow rate of the water was too high, causing a large amount of air to be drawn in the air gap. This also saves a lot of wasted water.



Edited 2 times.

Son of a gun. I was wondering what the tiny little thing was. As it were, I had installed everything and accidentally had water back up in to the unit and I thought THAT was what had caused the hissing, etc. Figured once that cleared, it would stop.

So... duh... those wee bits are LONG gone... however, luckily, because of the SHUTOFF VAVLE CONSUMING properties of the water here, I had actually installed an INDEPENDENT little ball valve in the feed... so when the thing fired up (it only makes noise when filtering) I got undersink and just cranked the ball valve down until the hissing stopped. It was by no means CLOSED so.... flow restricted. I should be all good.

Thanks for that bit of info.

It's a bit sad that a lot of times these "Amazon" products come with "instructions" that are not only cryptic, but not necessarily complete either.

Later!

BONE