Drainage Hose for Reverse Osmosis getting Black

I was hoping someone could offer advice about my GE Reverse Osmosis water filtration system. I've had the system for 1 1/2 years and continually struggle with the drainage hose. I've replaced it several times but it continues to develop this black goo on the inside of the hose after just a few months of use. Of course, I'm not concerned about the look but am concerned that bacteria is forming in the drainage hose which may be contaiminating the water filtration system. This may eventually make me and my family sick.

The drainage hose is the kind of hose one would use to run water to an ice maker - small clear plastic. I had previously ran the hose into the plumbing under the kitchen sink but it created too much noise in the kitchen. I then ran the drainage hose down from the bottom of the sink into my basement and into a utility sink. That is when I started to have this problem. The hose opens up into the sink and the water drains down the utility sink.

Any ideas why this hose consistentely gets black..or whether or not I need to worry about this black goo contaiminating the system? Any advice would be appreciated.

Fungus or Bacteria

It gets black because biological things are growing in the tube. It is a moist environment where things like to grow, and it is necessary not to have chlorine in the water that goes to the reverse osmosis membrane.

A lot of people get paranoid about a little chlorine, but residual disinfectant is necessary to prevent the kind of problem that you have. UV light and ozone provide no residual. Public water supplies are required to have at least 0.2 mg/liter of free chlorine, or an equivalent disinfectant, when the water comes out of your faucet.

As described by Bob, this is a normal consequence of filtered water, especiall the RO waste water. This is one of the ongoing maintenance issues with RO is to keep the drain clear.

I have noticed that the tube leading from my little undersink cartridge up to the tap gets cloudy. I simply replace that tube about every other filter change.

drain

The reverse osmosis system separates the drain from the potable water, so you should not have to worry about it. Especially since the drain hose has no pressure in it to "force" any drain water back into the purified water.

Thanks!

Thanks for all the great information and advice. This site is a wonderful resource!