Washing machine deficiency

Um. I can see that's the volume of the pipe. But this is flow - 10l/min. So 10 litres of water, plus the water already in the pipe between the heat source and the washing machine, has been through the pipe in that one minute.

Unless I'm very much mistaken; distinctly possible :-)

The question was whether the hot water would come from that sitting around in the pipe, or from the cylinder. If you draw 10 litres to do your wash, for that all to come from the pipe it would have to be 57m long. In my case the pipe is 7m, so that's 7/57=12% from the pipe and 88% from the cylinder, ie the water will be mostly hot. (others pointed out the amount may be less than 10l for a wash, so adjust numbers appropriately)

The flow doesn't matter: the WM opens the valve and starts filling; it closes the valve when it senses it has taken enough, ie it's based on volume not time. If you plumbed in a fire hose it would still use the same amount of water, just fill quicker.

Theo

It won't be that much. If your hot is at the minium of 60c and you are doing a 40c wash then how much it uses will depend on the cold temp.

The machine must ensure the temp does not go above 30c in case any thing is damaged by a higher temp.

Given the machine does not know how much cold it needs to run to get to the hot, or how quickly the hot and cold are going to flow, I can see why machines simply cold fill and then heat the water to the temperature they need.

You can get hot fill machines.

Dave

The hot fill will only be used on a couple of programs and even then the cycle is likely to perform a cold wash first in order to not to cook in some types of staining.

The most common wash programs will never use the hot water at all. Unless you are always using the most aggressive 90C cotton only wash then the payback probably will be never, compared to a cold fill only machine.

The tend these days is not for hot washes but for very much longer washing cycles at 40C, or under, using detergents working at 15C.

Mine is not 56m, but it is at least 60 feet or more. Diagonally across the loft of the extension at the rear of the house, then vertically down for two floors to the cellar ceiling, around the cellar, and finally out at waist height to get to the utility room. Running the hot tap there takes a loooong time before it runs hot.

My previous hotpoint was hot&cold fill. Unless I forgot I would always drain the cold water in the hot pipe via the sink tap before pressing start, you could hear from the difference in fill rate (mains pressure cold vs gravity hot) that it used both fill valves alternately on most washes, to get whatever target temperature the wash required.

But then, if you are on a water meter is that a saving?

Ah right, gotcha. My comment was in the context of a combi, which has no stored water.