[Greenbuilding] holding tank for solar hot water

[Nick Pine]

A plywood box lined with a single folded piece of EPDM can work, esp
if less than 4' tall.

STSS makes large circular tanks lined with EPDM, with a 170 F max
recommended temp. About $1500 for 1000 gallons.

The pressurized heat exchanger might be a $60 300'x1" coil of black PE pipe,
with a 140 F max temp. For DHW bursts, its 13 gallon volume and 3 minute
time constant can compensate for its ~60% effectiveness at 5 gpm. NSF pipe
is tested to 5X the pressure rating, eg 125 psi at 73 F, and loses about 10%
of the pressure rating for each 10 F temp increase, IIRC.

Nick