When the hot side of the valve is cold, the valve opens. When it’s hot, it closes. The pump pushes the cold water on the hot side through until warm water reaches the valve, then it closes, and the pump can just keep going without moving any water. As the water at the valve cools down again, the valve opens again.
With an aerator on the tap it’s not much more than a second of warm water so the wasted water isn’t really much volume at all - 100mL vs several litres.
I also have a separate drinking water tap which is really my only cold water application so a bit of water at 30° instead of 18° doesn’t bother me.
Yeah it’s confusing.
When the hot side of the valve is cold, the valve opens. When it’s hot, it closes. The pump pushes the cold water on the hot side through until warm water reaches the valve, then it closes, and the pump can just keep going without moving any water. As the water at the valve cools down again, the valve opens again.
With an aerator on the tap it’s not much more than a second of warm water so the wasted water isn’t really much volume at all - 100mL vs several litres. I also have a separate drinking water tap which is really my only cold water application so a bit of water at 30° instead of 18° doesn’t bother me.
Thank you Flax, this was a very useful explanation! I will look into it and figure whether I can install it in a suitable place in my bathroom.