Hi Gordon, I'll TRY to shed some light on this subject. I have, in My home, a Fisher-Pakel DD 605 dishwasher which uses VERY LITTLE water to do a load. I also have a TOYO instant water heater. The ONLY thing that I do is run the water in the sink until its hot, Then start the Dishwasher!!! I'm not sure how
other water heaters(instant type) work, But the TOYO holds,and keeps about 3 gal. hot all of the time. I also have customers with the TOYO water heaters and they don't seem to have any problems.