It's just so the cold water pipes sit in a pool of warm water. https://www.meanderhr.com/wp-content/uploads/2012/11/HXdrain-heat-recovery-shower-drain-heatexcha

It's just so the cold water pipes sit in a pool of warm water. https://www.meanderhr.com/wp-content/uploads/2012/11/HXdrain-heat-recovery-shower-drain-heatexchanger.jpg https://www.meanderhr.com/wp-content/uploads/2012/11/HXdrain... This is even simpler: https://warmduscher.de/produkt/warmduscher-original/ https://warmduscher.de/produkt/warmduscher-original/