Ideas how to save cold hot-water?

Hi
In my house I have a significant distance between my bathroom and water heater. Every time I'm taking a shower or need hot water, I have to keep the water running for quite some time before it gets hot.

So, I guess the most common approach would be to shorten the time until the water gets hot by installing circulation, smaller pipes etc.

But, I'm looking for advise on a different approach - how the cold hot-water can be saved in a smart way, instead of just flushing it down the drain. Maybe using some valves, temp sensors etc. The water can then be used for flushing the toilet, watering my garden or something.

I'm thinking both high-end and simple solutions are of interest. Anyone who has done anything like this and can share some ideas/experiences?

Thanks!

Zugarelli:
Hi
In my house I have a significant distance between my bathroom and water heater. Every time I'm taking a shower or need hot water, I have to keep the water running for quite some time before it gets hot.

So, I guess the most common approach would be to shorten the time until the water gets hot by installing circulation, smaller pipes etc.

But, I'm looking for advise on a different approach - how the cold hot-water can be saved in a smart way, instead of just flushing it down the drain. Maybe using some valves, temp sensors etc. The water can then be used for flushing the toilet, watering my garden or something.

I'm thinking both high-end and simple solutions are of interest. Anyone who has done anything like this and can share some ideas/experiences?

Thanks!

Actually, millions of people do what you are suggesting. There is gray water and black water. Black water goes to the sewer, as you are doing. All other waste water is gray water, your shower water, your discarded cold water while waiting for hot, etc. all go to a gray water tank.

When needed for irrigation of flowers, lawn, garden, etc. the gray water is pumped out to use.

Same scheme is used in all recreational vehicles with bath and kitchen. Black water and gray water.

So, NO ARDUINO is necessary. Just some plumbing work on your part!

Paul

No, what is needed here is white water diversion. That is potable water you are talking about throwing out - a cardinal sin. Rather than after the plughole, which you should be doing anyway, and probably already have more grey water than you need, store-bought thermostatic diverters installed in front of the bathroom divert initially cold water to a white-water tank. I recall they are quite expensive, and you might have to make a serious judgement about the actual location, depending on how badly planned the house was in the first place.

www.redwater.net.au

You may indeed also need to consider the piping. Don't expect to get much help on this from a plumber, you are more likely to get active opposition - which you should then studiously ignore. Talk to an airconditioning outfit instead. They should have 6mm pipe and good quality insulation, and that should serve one shower at 6l/min.

This is not an Arduino problem - or should not be.

try this
https://watersavingshowers.com.au/

You could do like hotels and motels do, have a circulation pump that circulates the hot water to the use point and then back to the heating tank so the supply line from the tank to the end point is always filled with hot water.

Run the water into a handheld pitcher 'til it gets hot. Use what you've collected to make coffee or throw in the washing machine.

Alternate solution: install a point-of-use / instant water heater in the bathroom.

Would not do that. Warmwater lines are prone to legionella, if not heated up on a regular base.