Monday, July 23, 2012

What a drip!

Although it's now nearly a month ago, I thought I'd share a little learning I received the first time we ran our dishwasher.  We had been watching the kitchen sink plumbing as previously there had been a tiny leak from the smaller half (nothing that a little turn of the wrench couldn't fix), but hadn't yet used the dishwasher. Thankfully we were watching, because as soon as the dishwasher began draining, there was a stream of water running down the dishwasher drain line from near the air gap. Having no idea how a  dishwaser drain is hooked up, I did a little research online to see if it was something I could fix myself, and learnes some interesting things along the way.

First things first, this is the proper drain set-up for a modern dishwasher.  The drain from the dishwasher is brought up to the air-gap before connecting to the waste disposal (if one is present).

So what the heck is an air-gap, and what does it do? 

It's the funny little chrome thing on the sink next to the faucet that you never knew what the heck it was.  The air-gap is a basically a mechanism to make sure dirty water does not get flushed back into the "clean" dishwasher system.  This is useful in case there is a sewage back-up in the drain system further on down the line. 

The old style of preventing back-ups into the dishwasher was by a system called a "high-rise loop" (left).   This system just involved elevating the returning dishwasher drain line above the kitchen sink drain.  However, this just increases the pressure needed to back the system up and doesn't eliminate the possibility of contamination.

The air-gap (below) involves a high-rise loop, but inserts an actual "air gap" into the system.  This way, if the main line were to back up into the dishwasher system it would reach the air-gap and spill out into the sink rather than going further into the "clean" dishwasher system. (Although sewage water in the sink is pretty darn gross too!)

Of course, thankfully all the problem was was just readjusting the clips and tightening the connection between the drain line and air-gap mechanism, but now you learned something!


Xaparro said...

Fantastic, Juan! Papi will be so happy that now we have a plumber in the family! The illustrations were very helpful. We don't have one of those airgaps. Should we worry or is it because we are up on the 2nd floor?

Juan said...

Well I think it really depends on where the back up is. If it's in the sink drain before it hits the main stack, then it would still back up. But I think these are more for when there is a large volume backup from the mainline, so I think in that respect you're in better shape.

I don't know what code is in Pennsylvania, but this is definitely required in California, our inspector checked for it when he went through. Although when I was researching this topic, it seems like many experienced plumbers think the high-rise loop is adequate and have never bothered to put in an airgap (I guess because it looks funny and takes up a spot on the sink where a hot-water dispenser or something else could be).

Camila said...

Are you sure you don't have an air gap, mom? We's what gurgles when your dishwasher is running. That is about as much as I understand--Juan, I must say you really have the mind of an engineer, figuring out how things work.

Juan said...

Well the Internet is an amazingly educational place, if you search long enough =)

I think I'd love to take some community college courses in electrical and plumbing or general contracting work. Was reading a book on wiring last weekend and learned so much, but the National Electrical Code is pretty extensive.

Camila said...

Hey--you should see if you can take adult education classes at your local high school. They had that in Davis and I took a car maintenance class. Maybe they have electrical/plumbing stuff.