Dishwasher plumbing....need advise

To be clear Joe, your references apply only to jurisdictions following the IRC. The original post is from a CA inspector, a state in which dishwasher-discharge without an air gap device is specifically prohibited.

In most cases, manufacturers requirements override model codes, EXCEPT when the code expressly prohibits a particular installation.

The California Code is quite clear and prohibits installation of the dishwasher without an air-gap device;

2010 CPC 807.4 No domestic dishwashing machine shall be directly connected to a drainage system or food waste disposer without the use of an approved dishwasher airgap fitting on the discharge side of the dishwashing machine. Listed airgaps shall be installed with the flood-level (FL) marking at or above the flood level of the sink or drainboard, whichever is higher.

Just curious how CA adopts codes. I’m assuming the CPC stands for Calif. Plumbing Code (a state code)? But the ICC website says that the State of CA has adopted the IRC:

What’s going on in CA? Again just curious. Please enlighten me.

Yes, CPC is the California Plumbing Code.

CA has always followed a modified version of the Uniform Code. The 2010 cycle of the CA Code has adopted portions of the International Code and will eventually phase-out the Uniform Code. However, CA modifies the Model Codes as they (CA Code Authorities) see fit. Even when/if the International Code is fully implemented by CA, there will be CA specific modifications. This goes for the NEC as well.

In addition, CA allows city and county modifications to the existing CA Codes, except where the CA Code is prohibitive, as with the previous example. So many cities (such as where I live) have been using variations of the International Code for quite some time.

Just for your information. Illinois plumbing code does not allow the dishwasher drain line to connect to food grinder (garbage disposal).

Section 890.770 Dishwashing Machines](

Domestic Dishwasher (Private Residence). When a domestic dishwashing machine drain line is connected to the house side of a trap from a sink, the drain from the dishwasher shall be carried up to the underside of the spill rim of the sink. Dishwashing machines shall discharge separately into a trap or tail piece of the kitchen sink and* shall not connect to the food waste disposal unit. ***

Glad I don’t live in CA or IL. That’s a crazy rule.

I agree. When properly trapped there should be no issue with drain at GD.

In Chicago an air gap devise is required but rarely enforced.

Reverse trap to rim line helps until drain backs up since water seeks its own level.

I think (yes assuming) the Disposal rule is because it is though all that old food material has more bacteria in it.

Something to discuss.

So here’s a good question for IL and CA folks: if we aren’t code inspectors and you think it’s a stupid rule, why write it up?

How many are under 18" ?
GE Consumer & Industrial

An air gap MUST BE USED if the drain hose is connected to waste tee or disposer lower than 18" above the floor level. Failure to provide the proper drain connection height with an air gap or 32" minimum, high drain loop will result in improper draining of the dishwasher, which may cause damage.

Drain Requirements
Follow local codes and ordinances.
• Drain hose must not exceed 10 feet in length.
A high drain loop or air gap is required. See below.
Drain Method
The type of drain installation depends on the following:
• Do local codes or ordinances require an air gap?
• Is waste tee less than 18" above the floor?
If the answer to either question is YES, an air gap (Method 1) must be used. If both answers are NO, either an air gap or a high drain loop (Method 2) may be used.Dishwasher install to disposal.jpg

Dishwasher install to disposal.jpg

I don’t think it’s a stupid rule. I have seen the results of “muck” from disposals backing up into the dishwasher drain line. It’s pretty disgusting. It also creates a horrendous smell in the dishwasher.

A properly installed air gap device eliminates the possibility of anything getting back into the drain line. Not allowing the connection to a disposal also eliminates this potential. So I agree with both “rules.”

A high-loop is only effective as long as the sink/disposal drains do not back up. If the sink happens to flood above the high-loop, contaminates will make it back into the line.

Jeff ,if you read my excerpt from GE above would you agree that ignoring local code voids the warranty?

(See bold text.)

In almost any instance, when the manufacturers installation requirements are ignored, their warranties are void.

So yes, I agree. Improper installation of the drain line may very well result in voiding of the manufacturers warranty.

This reason that Bob and Jeff acknowledged is good enough.

Yep,that is how I see it.

In my town we must look at this stuff and think about wording.
Example: NM cable being used in most of my area is not allowed and this is well known so Do I mention it is against code? :slight_smile:

Pex is not allowed in the city either so what is written?

Best way I have found is to mention a suggestion it be looked into otherwise you will not be actually helping your client even if you have every legal right to be snowblind.

Otherwise you also should ignore IRC codes and all other issues involving specs.

It has been mentioned on the forum we should go by state codes “only” if we are state licensed, but then again we are not code inspectors.:shock:
We all use the 4" baluster rule right?

Yes wording can be tricky. As Will says he bases it on “best national, or nationally recognized, building practices”.

Glad I don’t inspect in Chicago though, with copper plumbing, and all electric in conduit, and the new fad split faced block. :twisted:

Split block is becoming the old fad though they use it a lot on commercial which is fine.

Personally I have no issues if it is done right.

Will has some good advise however we all must think for ourselves and then decide.I mix advise,best practice and doing what is best for my client so if anyone does not like that …tough apples.
Never been one to follow the crowd myself…:slight_smile:

Remember you get sued by the client, not the code book. Hopefully neither.(big reason I like narrative report style)