This is not quite as simple as I once thought. Most modern washing machines are cold fill only. Having just the one inlet that connects to the cold water supply. You could run a pipe from the hot supply, but bearing in mind that most machines are quite a distance from the hot tank, the water will probably still be running cold as the machine fills up. Then as the machine reaches the rinse cycle it will start to use hot water to rinse. Thus wasting hot water. Modern machines do not use a great deal of water, and it is not heated usually above 40c. Some programs for delicate items need lower temperatures and if your water is coming in at 60C it will be too hot. So it is debatable whether using Solar hot water in the washing machine will be economical at all. There is a similar problem with the dishwasher. This is something that needs a bit of research. A smaller well insulated cylinder situated close to the machines, with a thermostatic valve and controller that lets water in only at certain times. Not at rinse cycles.

zanussi Zanussi2

A Eureka moment

On a really sunny day like today (11-10-08) it seems a shame not to use the hot water in the machines. We are making today more hot water than we can use. When the water in the panel is a great deal hotter than the tank there is maximum transfer of heat from the panel to the tank, so it makes sense to use as much hot water as possible when the sun shines. Our dishwasher is an old Zanussi DW 400 with an electro/mechanical dial on the front that whirs and clicks as it rotates. We always use program C, universal no pre wash 65C. When the machine starts it fills with cold water about 8 liters and it heats this water up to about 65C using electricity as it washes. After about 15 minutes this water is pumped out leaving the inside of the machine quite hot. Then the machine does two rinse cycles using much less water this time. The rinse water just gets warm from the inside of the machine as it does not get as high as the heating element. I wondered what would happen if I pre filled the machine with hot water from the tap. Would it fill with more water and overflow I worried ? So I tried it. I filled a plastic bucket with 8 liters (using a measuring jug) of hot water making a mark on the side of the bucket for next time. I started the machine half expecting water to pour out all over the floor, but it did not. There must be a float switch inside. The whole thing worked a treat. So I have found a way to use the solar hot water in this machine without extra pipes or controllers. Our washing machine ( Bosch WFF 1200 ) actually uses less water 6 liters. We nearly always use the same program at 40C.

1 I put the washing powder into the drum.

2 I put in the washing and shut the door.

3 I pour the hot water ( 6 liters ) at about 45 C in through the powder tray.

4 I start the machine normally.

This is working well at the moment. In a few years I think some machines will come with a special dedicated solar input.

Mark 2 method

1 I put the washing powder into the drum.

2 Pour the hot water ( 7.5 liters ) in through the door with a new plastic watering can.

3 Put in the washing and shut the door.

4 Start the machine normally.

5 For a 40C wash you need to put the water in a bit hotter if you have it. Today ( 08-04-09 ) ours was about 60C so I mixed the water in the can to about 50C. The drum and washing cools the water down quite a bit. As far as I can tell no new water was taken in at the start and I do not think the heater came on.

New Dishwasher today ( 11-06-09 ) The old Zanussi dishwasher has gone to the scrap yard at last. Has worked faultlessly for about 24 years. Was still going when I took it out. Just rusting away around the door hinges and starting to look awfull. Would have bought another Zanussi but Costco do not do them. Sent emails to LG,Bosch,Hoover,Hotpoint,and Zanussi enquiring about hot fill and pre-filling , but got no replies. Purchased the Hotpoint FDF 784P from Costco for £260.00 and will start pre-filling experiments soon. This new dishwasher uses much less water than the old one. Trying to pre-fill with hot water has not worked so far. I pre-fill the machine and when I start the program it immediately pumps out. This is a bit of a disaster , but would probably have been the same whatever model I chose. We usually only do a dish wash every other day luckily. The washing machine is on its last knockings also, so I will have to be more careful when we get a new one. A very simple machine is the idea I think. But there is hope. Just been reading the Hotpoint installation manual. It says at one part that the machine can be filled with hot water up to 60C. So I may install a dedicated hot water supply after all. And do away with the watering can. Finally got an email back from Hotpoint. Machine has to be connected to a cold water supply. Not very green. This advice conflicts with the installation manual .

( 24-06-09 ) Got no replies from washing machine manufacturers at all. So I decided to keep the old Bosch going for a while. I still believe that machines will soon appear with a dedicated solar input. Took about two hours to change the bearing, and cost £ 5.00. Machine now sounds like its new. Note. From a washing spare parts shop I was quoted £ 34.00 for two bearings and a rubber seal. The same thing on Ebay was £ 25.00 inc postage. The rear bearing and rubber seal were in good condition so I took the old front bearing along to a local business. J & M bearings at Grays Essex. They had the exact bearing in stock ( good make ) for £ 5.00. We did fancy a new washer, but decided to wait a while, and see what happens. This one is perfect for Pre-filling.


28-02-11 Old machine breaks down. Could have fixed it yet again but, with my wife's birthday comming up decided to get her a new one. A ( Bosch WAE24469GB ) takes the hot water through the door no problem. About 10 litres. Uses a bit more water than the old one. Have to fill the can to the top.

01-06-12 On sunny days now pre-filling the Hotpoint Dishwasher. Do a normal wash but press pause after about 5 minuts. Open the door and note the water level inside the machine. For my machine it is about 25mm below a metal seam. When the machine is finished empty the contents in the normal way. Then fill the machine with water using a measuring jug and make a note how much water it takes. 8 litres for example. Next time you do a wash. Start the machine a listen for the pump. It pumps for about 30 seconds with an empty machine. Then do a pause and open the door. Pre-fill the machine with your free hot water. Then shut the door and restart.


Above is a pictures of freshly opened boxes of soap powder. The powder is actually 150 mm from the top of the box. How do they get away with this. Think about all those half empty lorries carting this stuff about.


Do these machines encourage laziness around the house? Are there other ways to do washing and dish washing that do not need electricity?