I was told years ago by a plumber that you "don't really need" an
airgap for reverse osmosis filters (I was complaining about the drain
noise). He told me how to hook the hoses up to eliminate the airgap,
which I won't go into here because my question is: is this safe? Is
this airgap really only there for when my SEWER backs up into my sink?
If so I think I can live without it! Or does a sink clog backing up
present some sort of flowback danger to my RO unit? Thanks in advance.
I think you know the answer to your own question. Air gaps prevent
siphoning of waste water back into whatever is connected to the drain,
ie dishwasher, RO, etc. Most dishwashers are not installed with one,
though in some places code requires it. If an air gap is not used,
for dishwashers, the drain line is routed high to the bottom of the
countertop, to help prevent the problem. But that is not as good as an
For a dishwasher, I'd say it's OK. Mine is done with a high loop.
However for a unit that handles drinking water, I would want the air
gap and I would be surprised if it were not required by code.
waste water from mixing with potable water.
RO faucets on a sink have been sold for decades with air gaps in the faucet.
My RO output is plumbed solely to the refrigerator for Ice and Water.
My RO waste water goes to a sump pump that is common with the AC
Evaporator drain. That then pumps to the clothes washer drain. I get
pump noise every 10-15 minutes while the RO is refilling the tank, more
often if the AC is running. sump pump is in a tub that connects to a
separate waste water drain for AC only, in case the sump ever fails.
If you don't mind the possibility of your family drinking and eating raw
sewage then forgo the air gap. If the thought of trying to
decontaminate your filter system after such an event gives you pause
then install the air gap and live with the noise.
"people willing to trade their freedom for temporary security deserve
The issue is that we tap DIRECTLY to a cold water line under the sink.
RO drain water then flows DIRECTLY to the waste water drain in the
sink. This is the noise that was being complained about.
If the RO fails, then the possibility is STRONGER that kitchen sink
waste water contaminates drinking water than the risk of toilet water
making it into drinking water. Either situation is EXTREMELY
unpleasant and VERY unhealthful. But Sink drain water is much less
likely to contain E Coli bacteria.
RO membrane failure is rare, but possible due to over pressure (very
unlikely) or very hard source water clogging the membrane and possibly
rupturing it (also very doubtful)
When I had my RO draining into the clothes washer drain, I had to
carefully position the hose so that the constant gurgle of the waste
water would not distract.
I suggest that you check with your local code enforcement agency and
with the manufacturer of the RO unit. If either say you need it, then you
need it. clearly you would not have the unit if you were not worried about
clean water. Why risk it, follow the rules and instructions designed to
keep you safe.
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