Posted on behalf of Tom…
Having re read it, I think his design is wrong, because there is no atmospheric pressure tank for the blow off. Where his 13lb cap is on the Grenada tank, there should be a pipe just under the cap which leads to a catch tank, open to atmosphere. When the system heats up, the expanding water blows past the pressure cap. Then gets sucked back in when the water cools. On his design, there is nowhere for this blow-off water to go.