I know that all the heated water will be in the pipe in the compost but I do not know how long it takes to heat the water in the pipe once it has been used. Is there a recommended length of pipe to use for X amount of showers? I have read that plastic pipes decompose and give off smells and copper is not good for several reasons. Stainless steel would be expensive and hard to coil. Any advice on this system would be appreciated.