I have had the usual symptomatic water overflow out of the dishwasher air gap on the top of my sink countertop. After replacing the countertop with granite and relocating the air gap hole, I replaced the hose from the air gap to the disposal and insured there was no blockage in the disposal and new hose. Yet I have so much water pressure coming from the dishwasher that it shoots out of the air gap vent. I confirm the water is draining into the disposal from the air gap vent but it seems there is so much water or the pressure is so great the system can't handle the amount of water being discharged and backs up into the air gap. I've even looped the extra amount of hose from the dishwasher to the air gap above the disposal drain height to see if that would solve this. It did seem to take some of the pressure off of the water coming out of the air gap but it still spews out. After searching and reading all the posts regarding this usually common issue, I'm at a loss. Anyone have any ideas?

ballengerb1

Speedball1, our resident plumber, tells us he never uses air gaps nor do I. They are intended to prevent back siphoning but you can do the same with a high loop in the drain hose. Run the drain out of the washer all the way to just under the counter and strap it to the cabinet, then to your disposal. The problem you are experiencing should not happen but we don't know if you added a new washer or who did your plumbing. Somethings is causing a partial blockage, you did not accidently reverse the two hoses did you? The drain from the machine goes to the smaller of the two tubes of the air gap.

daveskee

Ok I just conducted a little experiment and now I have no idea what the problem is. I disconnected the large hose at the disposal so that it was still connected to the air gap vent. I put the unattached end into a bucket and started the dishwasher. When the dishwasher drained water and water came out of the larger hose unobstructed into the bucket, water still came out of the air gap vent, same as before!

Is it possible that the dishwasher is draining with too much pressure?

ballengerb1

Dish washer pressure can't get stronger than day1. It is the same dishwasher, right? The hose leading to the air gap from the machine should be nearly straight, no loop so cut it shorter. Is the air gap the original or did you replace it when the counters went in? There is a very slim chance that you have a bad air gap. They are so simple the chances are slim. I'd remove it and just strap the drain I discribed earlier in the post. They are a pain and Speedball1 says they aren't needed although some cities require them to be up to code.

daveskee

Haven't changed dishwasher. Same as when we moved in, but we were having this issue then too. I've replaced the original air gap with two new ones, the first the same style and the second a different style. Same result each time.

Hopefully someone might have an idea. I'd like to try and keep it up to code by keeping the air gap.

ballengerb1

So you've had this issue all along, not tied to the new counters. Do you know that your city building code requires a gap? Dave, code is for construction and you doing a DIY have a bit of latitude, take it out.

daveskee

Yes local code here requires the air gap. If I was staying in the house I'd solve it with your solution but we're preping to sell soon and it'll have to pass inspection so I'd rather take care of it per code. I also want to know for my own education why it's happening.

So if there's anyone else out there with any ideas, let me know! Thanks in advance.

iamgrowler

Are there any kinks in the 7/8" hose going into the disposal?

Are you using the correct inlets and outlets on the air-gap?

The smaller inlet takes the hose from the dishwasher and the larger outlet gets the hose going into the disposal.

Also, check the inlet on the disposal to be sure the plug has been completely removed.

ballengerb1

Growler's correct about checking the disposals knock out plug, seen many still partially attached. However you said it still happens when you put the discharge hoes into a bucket. Since it was a new hose I'm stumped on this problem. Before we yell uncle please double check the two hoses going to the air gap. Growler and I both mentioned the smaller hose goes between the washer and the air gap. Sorry I could not solve this issue Dave.

daveskee

There are no kinks in the 7/8" hose and the correct outlets on the air gap are hooked up correctly. Small inlet from the dishwasher and larger outlet to the disposal. Knockout plug is not present as I've reached into the disposal and felt the open hole with my finger. I've even put a small screwdriver into the inlet and it came through into the disposal freely. I even felt the water shooting into the disposal from the 7/8" hose inlet as the dishwasher drained. But listen to this, as the water is shooting into the disposal as it should, water is still coming out of the air gap! There seems to be to much pressure. So much so that if I take off the metal cover on the air gap, the water shoots up about 8-10" out of the top of the air gap.

As far as I know, you can't regulate the drainage pressure from the dishwasher.

Could a blockage in the dishwasher or dishwasher drainage line cause increased pressure? I assume it would just do the opposite and cause less water pressure.

Thanks for the tips guys but I think I've thought of everything that's been suggested so far. I can't believe no one else has had this problem. Well I'm holding out hope that this thing won't beat me and am still open to suggestions if there are any others out there!