I'm confused about the air gap issue after reading the forum. I was told I need air gaps on my dishwasher, sink, ice machine, etc meaning no direct connection to sewer line in my coffee shop. I was going to install these air gaps under the raised building thereby elinminationg the possibility of a back up flowing all over the floor under the cabinetry. If there is an opening in the line under the house how does this impact the placement and necessity of p traps and venting. Can someone help?

All p-traps need to be vented. I don't know your codes, but you can run indirect wastes only so far. You can eliminate some p-traps at fixtures. I doubt you can have one house trap-air gap under the building that all fixtures dump into.

by the UPC you can only run 5 foot of indirect waste without a p-trap and 15 foot before you need a vent. You drain kitchen sinks ect. into floor sinks so you can clean the floor sink out of food waste, therefore it needs to be accessable and exsposed to see every thing is working properly. Your local heath department will give you all the requirements of the area you are in, for food prep they are the ones to set the standards and most cities are different in what they require.

What the health dept is trying to avoid is a situation where, say you have a minor clog, sewage backs up into the ice machine, contaminates the ice, the clog clears itself (happens sometimes) and you don't know a thing about it. Would you want that ice in your drink? Around here fixtures that may hold consumables are drained indirectly, into floor sinks, which are trapped & vented & connected to the building drain.

I like the fact that I don't get sick from most American restaurants; the health dept codes usually have good reasoning behind them.

-Steve G

First you need to understand what is ment by an air gap. This is the free air space between the end of one drain and the opening of another. As posted this prevents the sanitairy drain from backing up into fixtures that are used for food preperation or human consumption. If the indirect waste is installed under the building and the drain was to back up you may never know it, therby flooding the under side of the building. What is implied is that you have a receptor in the floor, most commonly a trap under this receptor and a vent if nessasary. The drain from the fixture drains to this receptor and discharges above the receptor with a free air space. This is a complicated process to explain to a non plumber, it would be wise to contact a plumber for these corrections. This is what plumbers do, protect the health of the nation.

There should not be any confusion. You should have a device known as a floor sink under, or in the area of the sink. Those three fixtures must have their drains piped to that floor sink, and then terminate at least 1" to 2" above the rim so that the floor sink can overflow without the water touching the drains for those three devices. It has to be visible, not under the floor.

Thanks. It is complicated for a non-plumber and I've discovered I'm going to have to find a plumber who knows more about commercial applications in my area. I'm very concerned about having this done properly as it is a public health issue. Unfortunately, I've learned that just as in any field, not all plumbers know their craft equally. My small town inspector is loaded down because he is the only inspector and inspects every trade. He is helpful but also seems to have limited experience with commercial/food prep applications. Your responses have confirmed my degree of ignorance regarding this issue.

One more question please. Would the floor sink then drain into the grease trap, then to the main sewer line?

You don't say where you are from, but most locals will not allow a non plumber to do plumbing on a commercial job, especially a food establishment. There are alot more safeguards than just air gaps. I am sure you will be required to have a reduce pressure backflow device. You may well need a grease trap sized to your specific needs. It would be folly to try and do this yourself. Your liability insurance may not even cover if you did your own plumbing...
Deb
The Pipewench

Sue,

I'm from southern Louisiana restoring a building in excess of one hundred years old, listed on the National Register of Historic Places. I'm trying to get an understanding of these principles to effectively communicate with my plumber. I don't want to remain ignorant and rely solely on one person's advisement regarding design of the system. That's why I've come to you, a group of knowledgable experts in the plumbing field. This way when my plumber advises me regarding design, I at least have some small basis of understanding.

Deb,

I'm sorry I addressed my reply to Sue. It was meant for you.

It could depending on the sink's usage. If it is used for dishwashing then it should go to the grease trap.

since you are in louisiana(Gods country) you can contact the state plumbing board in Baton Rouge and ask for the name of the state inspector in your area. he will look after your best intrest in this matter as far as code requirements.

Thanks everyone; you've been great.