ᐅ Installing ball valves directly on the thermal storage tank?

Hello,

Since I now have to drain my 800-liter (210-gallon) stratified storage tank due to the installation or modification of a hydronic solid fuel stove, I am wondering if it would make sense to install ball valves on the four inlets and one outlet of the tank.

My concern is that the ball valves (1” Kirchhoff nickel-plated brass) might leak due to the expected high temperatures.

One of the connections is linked to a Paradigmar solar system, which operates with “dead water,” meaning there is no heat exchanger to improve efficiency. However, in winter, this setup always pumps some energy into the solar system. In summer, it sometimes pumps water at 80–90°C (176–194°F) into the storage tank.

Does anyone have experience with this and can share advice?

Thanks in advance.

Best regards

Personal experience: no.
Some knowledge: yes.
I share your concern that the seal might eventually have issues with the high temperatures. I would recommend choosing a fitting designed for that purpose.
The ball valve does not provide any safety function—neither against malfunction nor in terms of scald protection. Of course, you can install it at home, but I would not feel comfortable with that.
A tool-operated heat-resistant valve with a screw cap as additional protection seems to me a better solution—and not significantly less convenient for the rare occasions when it is needed.

I have reviewed the manufacturer’s system online. According to the information, warm water must be circulated through the collectors in winter for frost protection, as this system operates without a heat exchanger and therefore without glycol (antifreeze). So, forget about using ball valves for these connections. What is an advantage in summer becomes a disadvantage in winter.

I am familiar with systems that also operate with regular water, called drainback solar systems. In these, the collectors simply drain or remain dry when no output is expected, both in summer and winter.