Sun, 31 May 2026 06:05:33 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309927#Comment_309927 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309927#Comment_309927 Thu, 25 Dec 2025 09:52:44 +0000 minisaurus
I can’t see any downsides to doing this?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309928#Comment_309928 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309928#Comment_309928 Thu, 25 Dec 2025 10:13:33 +0000 fostertom https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309930#Comment_309930 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309930#Comment_309930 Thu, 25 Dec 2025 11:42:14 +0000 minisaurus https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309933#Comment_309933 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309933#Comment_309933 Thu, 25 Dec 2025 12:54:18 +0000 fostertom https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309934#Comment_309934 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309934#Comment_309934 Thu, 25 Dec 2025 13:39:05 +0000 owlman I think the machine has to be designed to take hot water as some machines have cold rinse or pre wash cycles, so not just a simple matter of swapping cold input for hot. I'm guessing you'd need both hot and cold inputs, with a machine controlled thermostatic valve on the hot input to allow progressive wash cycles.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309937#Comment_309937 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309937#Comment_309937 Thu, 25 Dec 2025 17:23:18 +0000 Peter_in_Hungary
Apart from that modern machines use very little water and depending upon your pipe sizes and distance from the DHW source to the machine you could find that the machine has reached its water level before the pipe has heated up and can deliver hot water to the machine in sufficient quantity to make any difference. The machine then does its cycle pumps out and fills again,by which time the water in the pipe and the pipe has cooled down. IMO the probability of marginal benefit is high. If you have a tap close to the relevant machines run the hot tap and see how many litres of water flow before usable hot water emerges and then compare this to the amount of water per machine fill to level.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309938#Comment_309938 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309938#Comment_309938 Thu, 25 Dec 2025 19:02:22 +0000 fostertom https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309939#Comment_309939 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309939#Comment_309939 Thu, 25 Dec 2025 20:19:07 +0000 minisaurus Posted By: Peter_in_HungaryWot owlman said above +1.

Apart from that modern machines use very little water and depending upon your pipe sizes and distance from the DHW source to the machine you could find that the machine has reached its water level before the pipe has heated up and can deliver hot water to the machine in sufficient quantity to make any difference. The machine then does its cycle pumps out and fills again,by which time the water in the pipe and the pipe has cooled down. IMO the probability of marginal benefit is high. If you have a tap close to the relevant machines run the hot tap and see how many litres of water flow before usable hot water emerges and then compare this to the amount of water per machine fill to level.

That’s a really good point; I think your suggestion may be the reality; that the water isn’t warm by the time its filled the machine; I shall test as you suggest :)]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309945#Comment_309945 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309945#Comment_309945 Sat, 27 Dec 2025 08:38:20 +0000 passivhausfan https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309946#Comment_309946 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309946#Comment_309946 Sat, 27 Dec 2025 09:03:41 +0000 revor Posted By: passivhausfanIn North America, where they do connect to the hot, the advice is to run the tap hot first before you switch them on.

Somehow in the land of extravagance I am not surprised. Many years ago I saw a documentary about water. Therein contained a piece on the amount of water taken out of the Colorado and the amount of water lost out of Arizona swimming pools in its hot climate. I forget the numbers. There was a comparison of the American extravagance to that of those in much of underdeveloped world, it changed my approach to the use of water and how much energy I use to heat it.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309955#Comment_309955 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309955#Comment_309955 Wed, 31 Dec 2025 05:49:23 +0000 Gareth J https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309958#Comment_309958 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309958#Comment_309958 Wed, 31 Dec 2025 10:38:13 +0000 dathi https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309960#Comment_309960 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309960#Comment_309960 Wed, 31 Dec 2025 11:14:00 +0000 Peter_in_Hungary Posted By: dathii have solar thermal so a lot of hot water in summer i add the hot water through the front tray of washing machine at the beginning of the cycle i use couple of 2 litre plastic milk bottles as i have a sink next to washing machine
I presume by ' at the beginning of the cycle ' you mean after the starting pump out phase you open the door and pour in the hot water then press start to continue the program.

As a matter of interest how much water is drawn before hot water arrives at the tap?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309962#Comment_309962 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309962#Comment_309962 Wed, 31 Dec 2025 14:47:31 +0000 owlman https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309963#Comment_309963 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309963#Comment_309963 Wed, 31 Dec 2025 16:19:36 +0000 dathi https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309993#Comment_309993 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309993#Comment_309993 Wed, 07 Jan 2026 13:33:30 +0000 bhommels Reading through the manual of our Bosch dishwasher, it is specified to take in water at any temperature between 5 and 50 C (going against what the sales people tried to tell us)
The dishwasher measures the temperature of the incoming water and then decides how much post heating is needed, contrary to older machines which would heat for a set amount of time.
I measured the consumption: a cold feed ECO cycle takes 1.5 kWh, a hot feed ECO cycle less than 0.5 kWh. For an automatic cycle, the consumption is higher and the savings bigger, depending on the state and quantity of the dishes.
Since modern machines fill up their internal reservoir and recycle the water in there for the wash, and then again the rinse cycles to be more economic, pipe lag is less of an issue.
Hope this helps.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309998#Comment_309998 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=309998#Comment_309998 Wed, 07 Jan 2026 17:32:15 +0000 fostertom https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=310000#Comment_310000 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18387&Focus=310000#Comment_310000 Wed, 07 Jan 2026 17:42:12 +0000 WillInAberdeen