Does a Dishwasher require a Air Gap?

Inspected a Home and the dishwasher looked like a brand new recent install.
I ran the dishwasher through one complete washing and all seemed ok.
Are Air Gaps required ?


Yes they are required but less than half of new construction has a air gap and almost none of the older.’
Here is my report comment.

Airgaps are now standard equipment to assure a separation between
supply and waste water. It is advised that either an airgap or a high loop
be installed between the dishwasher and the waste connection

Some models have it built in but that will not be determined by you .

Not usually.Note that P2717.1 is speaking about the water supply to the dishwasher. The following codes are speaking about the waste discharge from the dishwasher.**

2006/2009 IRC

P2717.1 Protection of water supply.** The water supply for
dishwashers shall be protected by an air gap or integral
backflow preventer.

**Commentary: **Residential or domestic dishwashers must conform to
ASSE 1006. This standard includes protection of the
potable water supply against backflow
. Units conforming
to this standard possess backflow protection consisting
of an internal, integral backflow prevention device.
Where a unit does *not *meet this standard,
protection must be provided by means of an air gap.
Section P2902.3.1 mandates an air gap.

** P2717.2 Sink and dishwasher.**A sink and dishwasher are permitted
to discharge through a single 11/2-inch (38 mm) trap.
The discharge pipe from the dishwasher shall be increased to a
minimum of 3/4 inch (19 mm) in diameter and shall be connected
with a wye fitting to the sink tailpiece. The dishwasher
waste line shall rise and be securely fastened to the underside of
the counter before connecting to the sink tailpiece.

**Commentary: **Dishwashing machines may connect directly to the
drainage system and do not require an indirect connection
by drainage air gap or air break.
The direct
connection is acceptable, because the potable water
supply is adequately protected against backflow. This
section requires that the waste line be looped as high
as possible and be securely fastened to the underside
of the sink rim or countertop to minimize the potential
of waste backflow into the dishwasher unit (see Commentary
Figure P2717.2).

**P2717.3 Sink, dishwasher and food grinder. **The combined
discharge from a sink, dishwasher, and waste grinder is permitted
to discharge through a single 11/2 inch (38 mm) trap. The
discharge pipe from the dishwasher shall be increased to a minimum
of 3/4 inch (19 mm) in diameter and shall connect with a
wye fitting between the discharge of the food-waste grinder
and the trap inlet or to the head of the food grinder. The dishwasher
waste line shall rise and be securely fastened to the
underside of the counter before connecting to the sink tail piece
or the food grinder.

**Commentary: **This section permits a single 11/2-inch (38 mm) trap
to receive the discharge from a sink, dishwasher and food
waste grinder. The discharge piping from the dishwasher
must be a minimum size of 3/4 inch (19.1 mm) and connect
to a branch tailpiece of a kitchen sink or directly to
the food waste grinder. For the same reason discussed
in the previous section, the dishwasher waste must rise
and be securely fastened to the underside of the counter
before connecting to the branch tailpiece or food waste
grinder (see Commentary Figure P2717.2).

Air Gap on Discharge is Required.
Sometimes built in to the Appliance

You guys need to re-evaluate what you’re interpretation of the code.

3 ways to do a dishwasher drain line correctly:

  1. Air gap
  2. Run in from bottom of cabinet and looped above discharge point and secured and back down.
  3. Run in from top side of cabinet above discharge point and back down.

Some cities require air gap only. Some cities want to see the loop and some are okay with either 3. Crazy!!

I very rarely see them. I think it will depend on where you live.

For Delaware (State, New Castle County) Inspections, I find Air Gaps (Physical presence) is required
In Pennsylvania, drain loop or internal to Dishwasher is Acceptable.

Yes, a gap or a loop.


Perhaps they made something up or you have an uninformed code inspector. It seems Delaware and New Castle County use the IRC.

New Castle County has recently adopted the ICC 2006 International Codes.”

Whether code or not does not really matter. The reason for the drain loop or anti siphon is to keep grey water from the sink backing up into the dishwasher. I have seen many a floor flooded from a large amount of water being dumped down a drain ending up in the dishwasher and if ajar, flooding the floor or, if closed, flooding the floor when opened.

If I see no drain loop in a dishwasher exhaust line during a home inspection, I call it out and explain why.

So Builders have been installing them for No Reason?

No Worries,

Delaware is the Only Place that I See Physical Air Gap Provisions at the Sink
Never in PA

So Builders install in DE when NOT Required
Who ever would have Thunk?

$12 a home…
lots of profit lost… :frowning:

air gap.jpg

They’ve probably gotten accustomed to listening to the ignorant code inspector and never challenge it. Read the code above and you tell me whether or not it’s required.

Thanks for the Code Reference
not so Many Inspections in New Castle DE but I do quite a few…

Generally Inspect Same as PA
Delaware is the only area
where I Consistently Find Air Gaps
installed for Dishwashers…

Never in PA…

Isn’t this required drain line installation for the purpose of creating an air gap?

I know what they are and what they do, but you know what? In 40 years of building, I still haven’t come across one of those in any kitchen with a dishwasher, Residential or commercial. hmmmmmmmmmmmm:mrgreen::wink:

I have recommended installation for every home that I have Inspected in Wilmington DE (where missing) and have never been questioned…

Recommend that in PA, and my Phone would be ringing by Contractors asking “wtf?”

:);)You must be making friends with contractors. :mrgreen:

I recommend one even if there is a loop. Both prevent water from back flowing into the dish washer. But when the drain becomes clogged and someone starts using their trusty plunger it forces the water and all that nasty stuff over the loop.