I feel like it's probably pointless. The dishwasher will be full of water before the hot water starts coming out the pipe. Depending on how far the dishwasher is from the water heater I guess.

▲

SoftTalker 11 hours ago | parent | next [-]

In most kitchens I've seen, the dishwasher is pretty close to the sink. In fact the sink and the dishwasher often share a shut-off valve. So if you run the water at the sink until it's hot, then start the dishwasher, it will get hot water.

Problem is, that most dishwashers have a prewash and a main wash. By the time the prewash is finished and the main wash starts, the water in the supply line will have cooled off quite a bit.

▲

doubled112 9 hours ago | parent [-]

Not just the shut off. My dishwasher's drain hose goes up into the sink's drain plumbing much higher than I would have thought.

This almost made a mess when the sink was clogged and the dishwasher tried to pump the water out but had nowhere to go.

▲

tguvot 8 hours ago | parent [-]

You can install airgap for this. In usa building code mandates it on multiple states

▲

olyjohn 8 hours ago | parent [-]

Is that the point of the air gap? I can't even get a straight answer from plumbers on what it's for. I don't see how that could possibly help with a clogged drain, just seems like a secondary point for the drain water to come out.

▲

SchemaLoad 7 hours ago | parent | next [-]

I'm fairly sure the point of air gaps on drainage is to prevent sewerage water from backing up in to appliances if the sewerage line is blocked. It will instead spill on the floor where it will be more easily noticed and cleaned.

	▲	db48x an hour ago \| parent \| next [-]
		That is exactly why they are required in restaurants. You wouldn’t want the sewage to back up into a sink where food or dishes might be.
	▲	throwaway173738 4 hours ago \| parent \| prev [-]
		That’s exactly what it’s for. If you block the sink drain and fill it with water, you can have water flow down the dishwasher drain hose and into the sump in the dishwasher. If that happens during the rinse cycle you’re rinsing with grey water.

▲

bcoates 6 hours ago | parent | prev [-]

Pumped out water has to go somewhere . With the airgap, it will either back out your garbage disposal or pour out your airgap into the sink basin, depending on the location of the blockage.

The airgap causes the pump to be physically incapable of backfeeding the drinking water supply with dishwasher waste

	▲	tguvot 5 hours ago \| parent [-]
		iirc its less about contaminating drinking water (there is a valve and pump to get through. rather tricky) and more about waste getting into dishwasher during cycle and you getting contaminated dishes. my wife once decided to dump into garbage disposal a bunch of uncooked broccoli at once. it clogged garbage disposal and drain. when i tried to unclog it with plunger it backed into dishwasher (was hooked directly to garbage disposal bypassing airgap). took me hour to get everything out of dishwasher.

▲

SAI_Peregrinus 8 hours ago | parent | prev | next [-]

Thus the video's advice (also in my dishwasher's manual) is to run the water from a nearby sink until it's hot before starting the dishwasher. Because it helps significantly to get hot water at the input when US dishwashers are limited to 1200W of heating.

▲

db48x 11 hours ago | parent | prev | next [-]

You should actually watch the video so that you can see the graphs; it’s not pointless.

▲

pastor_williams 10 hours ago | parent | prev | next [-]

When I do the dishes I hand wash those that can't be put in the dishwasher before I start the dishwasher. This ensures that the water that goes into the dishwasher is already hot.

▲

cwillu 10 hours ago | parent | prev | next [-]

“16:12 The importance of purging cold water from the line”

▲

Freedom2 10 hours ago | parent | prev | next [-]

I don't think the dishwasher will be "full of water" as it doesn't actually fill up - rather, it only uses 2 gallons maximum per cycle, about the amount that would be the bottom of basin of the washer.

	▲	SchemaLoad 10 hours ago \| parent [-]
		That's what I meant. The water drawn from the dishwasher is small enough to not even purge the cold water from the line in many houses. So you would just be wasting heat by filling the pipe with hot water while only taking the cold water from it.

▲

tguvot a day ago | parent | prev [-]

https://en.wikipedia.org/wiki/Circulator_pump#Use_with_domes...

▲

Gigachad a day ago | parent [-]

This seems like something that only makes sense when water is scarce but electricity is cheap. You’d be constantly losing heat to the poorly insulated pipes.

	▲	Scoundreller 5 hours ago \| parent \| next [-]
		And you're fully losing heat if you dump lukewarm water down the drain (instead of cycling it back to the heater) to eventually get hot water.
	▲	maxerickson 15 hours ago \| parent \| prev \| next [-]
		People who do it more or less don't care about the price of energy (except maybe in the abstract). It's for comfort and convenience.
	▲	tguvot a day ago \| parent \| prev [-]
		I have all hot water pipes insulated in my house