I want to build a solar hot water system, using a pillow bladder. Can this be done?

Question:I live in Philadelphia Pa. in a 3 story condo. The roof is flat. We have 21 units and the cost of heat and hot water is $ 100,000 per year. Can I preheat the water in a 50 -100 gallon black bladder placed on the roof?

Answers:
Yes you can, but its not a very good idea. Solar panels are typically used for the purpose. They consists of small copper pipes and fins that collect the heat and transmit it to the water in the pipe. Think small increments here, like your coffee pot. The bladder is a big ball of water. The edges would get warm while the middle stayed cold.

There are other problems. You'd have to connect it to the water supply which is under pressure. Does it have connections for that?

Finally, you may be putting more weight on the roof than it can bear. I'd hate to see that bladder in the middle of your living room.