lemmyng@piefed.ca 2 weeks ago
Yes, as many others have said, there is an explanation for running the hot water before turning on the dishwasher.
However, your partner is wrong. The purpose of running hot water is to prime the hot water pipes. Once that’s done you can go ahead and wash your hands with cold water, because the hot water pipe is already full of hot water.
4am@lemmy.zip 2 weeks ago
You can run a mix of hot and cold water all you want, if the hot water is on, it still primes the hot water pipes with hot water; they don’t mix until they join in the faucet itself.
Running the hot water at the faucet will fill the hot water pipe with hot water (hasn’t had time to sit and cool down) so your dishwasher’s initial pre wash cycle has a higher temperature water to begin with as it draws from that same pipe; you’re not starting with slightly cooler water and waiting for the heating element to bring it up to temp (at least not as long, usually dishwasher water is slightly hotter than water heater temp).
Running cold water at the sink does not cool the dishwasher’s intake water down. Cold water isn’t mixed with hot until it’s already in the faucet (after the valves you control at the faucet itself). As long as you run the hot until hot water makes it up to the sink itself, you’re golden no matter what else is going on.