My cds has an adjustment for heat, built seems to be stuck open. I’m very impressed with the heat the CDS punps out.Most direct drives get whatever temperature the engine runs at. Not really any need to regulate the heat unless you don't want hot water for some reason but the Cleanco and hydramasters have had a control that bypasses the heat exchangers. I disabled it on my CDS as it was leaking. My Cleanco has an adjustable bypass so you can get less heat or no heat at all. Unlike exhaust heat exchangers, there is no need to bypass to the waste tank