Dishwasher connection to U is at about same >level as bottom of connection out of U to drain line.
>Sorry but I do not understand the above.

I double checked this. The dishwasher drain hose is actually connected almost an inch below the level of the top of the U trap. Whereas the Frigidaire instruction sheet (see Figure 5 in attached) says "entry must be above trap".

>Here is a good install sheet that should also apply to your unit.
>http://products.geapplia...DF&Name=31-30515.pdf

Thanks for the install sheet. The Frigidaire sheet does not mention minimum heights. However, my drain tee is 16" above the floor, not the 18" minimum required by the GE manual. The drain hose does go up to 32" as required. Interestingly my drain hose goes down to the floor between the drain tee and the top of the loop, so it always has water in it. Could that be a problem?

>Has the U trap been checked, it could be partially clogged.
Yes, I checked, it's clear.

>If the sink is far from the vent stack you may have to add an air gap to >the dishwasher drain hose. This will not only help prevent back flow into >the dishwasher, it will let air into the drain so that your sink should >empty faster.

This is a rehab apartment in an old (built in 1900) New York City apartment building, so I don't know how far the sink drain is from the vent stack, could be 2 feet, maybe 12 feet. Also the counter is stone with no holes for air gap.