Bought 30-year-old mfg home in Aug '08. Before operating dishwasher, replaced non-functioning disposal. Both dishwasher and disposal operated just fine until last week. Now water rushes out overflow valve up on top of sink during last 15-20 seconds of dishwasher drain cycle--this did not happen before. Since it didn't happen before, cannot assume any plug in connection point from disposal to discharge hose. Replaced discharge hose from disposal to air gap today. Then ran dishwasher--here comes the water out the overflow. Audible water flow from dishwasher through air gap indicates no blockage (and there was NO blockage in discharge hose that was removed). Air gap seems to not have blockage either. Drain system is kept healthy by flushing monthly with Liquid Plummer gel. Any clues as to what is happening here? Need assistance ASAP...

When you installed the new G/D did you completely removed the knock out plug from the G/D, it sounds like you did, and you say the hose from the dishwasher to the Air gap and the hose from air gap to G/D are clean not blocked.

If every thing is good then it looks like the dish washer discharge pressure is high and you have a partial clogged drain.

You can remove the "J" bend from the trap and snake the drain line, (see image). You will run into a 90 degree bend about 8 inches in but once around that you only have to put out 6 more feet of cable. After, flush with hot water.

If that would not help then I would recommend to get red of the Air Gap, and install the high loop, see the images below, Good Luck.

John

I would check the hose from air gap to garbage disposal. Make sure disposal knockout plug was completey knocked out. Let me know what you find.

Great advice from Afaroo. I would get rid of air gap and use the high loop as shown in his pics. Im not so sure about the plugged drain. I did think about it, but is seems like if it were a plugged drain(beyond garbage disposal) that the water would be backing up in sink before coming out of the air gap above the sink. I could be wrong. Just the way I see it. I would recheck both line from dw to ag and from ag to good. If all is well, get rid of the air gap. Please let us know what you find either way. Good luck and take care.

Hi Mygilrsdad,

The water from the Dishwasher goes up to the Airgap and then goes down to the G/D if the plug is not removed or partially plugged the water will over flow from the Airgap to the sink, Thanks.

John

Do as Afaroo suggested: make sure you have no plug in G/D inlet or that the inlet is not plugged with food. Also, you may want to check the hose between Air Gap and G/D. If it is kinked, or has any food remains in it - it will inhibit discharge and cause overflow through air gap.

Hi Mygilrsdad,

The water from the Dishwasher goes up to the Airgap and then goes down to the G/D if the plug is not removed or partially plugged the water will over flow from the Airgap to the sink, Thanks.

John

Yep I'm with you on this, I was questioning whether augering the drain past the trap would do any good. If blockage were downstream of garbage disposal, I think the water would come up in sink before coming out of air gap. Are we on the same page, or am I reading a different book.lol.

Hi lee,

Yes we are on the same page, in reality yes if the drain is clogged water should come out to the sink, but it has happened that water has over flowed to sink from the Airgap with the drain clogged, I suggested to snake the drain, Thanks.

Regards,
John