Hot Water Loop Pressurizer

We have a solar hot water system that shares the closed loop water with our house heating boiler. That way the domestic hot water can be heated with the main house boiler, two birds with one boiler.

Anyway, this system is from the 1980s and there's now a very slow leak in one of the pressure or air relief valves somewhere in the system. I couldn't find it, I think it's intermittent depending on water temperature.

Anyway, if the system loses pressure there's a chance of damaging one of the three Grundfos pumps (also from the 1980s) or the boiler (much newer). Best case is it simply stops heating, not good waking up to a cold house in the winter.

So, what to do? The system doesn't want a lot of pressure and I didn't want to do any fancy plumbing. ** IDEA **

I used a 12V pump intended for marine/RV water systems. It has a built-in pressure switch, it turns on at about 30psi and off at 35.

The suction side has a filter screen to a hose stuck through the lid of a 1 gallon anti-freeze mix bottle.

Hook it to a 12V AC adapter and it works! Been there a couple of years, still working on the same jug of anti-freeze but the system has never lost pressure since!

Here's pictures of the pump, pressure gauge, and the anti-freeze bottle with filter screen.

Attachment 34846

Attachment 34847