I was told that you were supposed to keep them running all day and only use a bypass into the tank when driving between jobs as stopping the water with a tap or univale will damage the unit.
I wasn't sure so thought I'd ask especially now as it will be getting colder.
I wish my memory was better, but under normal flow conditions (3 on our Varistreams so about 30 on Spring controllers), we were running at a pressure of just less than 50psi when I did fit a pressure gauge on our delivery hose. Sorry, but that was over 15 years ago, probably longer. Granted, we were still on pencil jets and minibore hose, but we were also using cold water. Hot water will require less pressure for the same flow rate.
Remember, the first Shurflo pumps we were using were rated at 65psi and we didn't have any issue working with a 40' pole fully extended.
Back in 2019 there was a windie on the other forum (P & F) who reported the following:
"This is self built, air heater to water heater conversion, once the pole is turned off the water diverts to a 50 psi pressure relief valve and then back to tank
The way I have it set with my simple pump controller pictured earlier means the pump draws 2.5 amp with open flow and 3 amp when the PRV is in use."This means the pump pumps water through the heat exchanger all the time. When you shut the flow off with your tap or Univalve the hot water is diverted back to the tank. This keeps the boiler working.
Simply you tee off the hose to the hose reel to the inlet of this pressure relief valve. The other end of the pressure relief valve is connected to the tank.