In most solar hot water systems, the water that is going through the solar conductors is potable and is the same water that will go into the house system directly. Generally, the storage tank is connected to a water heater, for backup purposes, and from the water heater through the house. In this system, the solar panels are made of glass. If the temperature in the area where the system is going to be used can drop to below 38 degrees farenheit, then a “draindown” system should be used that drains the water out of the conductors into the storage tank to prevent the glass panels from freezing and breaking. This is a critical part of the whole system, so don’t skimp here, get a good one. This part of the solar hot water system will not have to do anything for months on end, but when the temperature demands it come on, it has to work the first time.