This time, the tanks are really done and it’s time for the dreaded leak check. Van’s lists a couple of different options for pressurizing the tanks just enough to spot leaks with soapy water, while not rupturing the tanks in the process. I chose to build manometers for each tank and pressurize them together; if the water level in the manometers tracks together as temperature and air pressure changed, I’m assuming that the tanks probably aren’t leaking. That, plus the usual spraying of soapy water should be sufficient. Here’s the setup…

So how did it work? Pretty well, actually, once I sealed up all the expected leaks around filler caps, sump valves and vent lines. The temperature in our garage goes up and down quite a bit when the furnace/hot water heater comes on, and the manometer levels for both tanks matched over a full day’s worth of monitoring. So I cleaned off the soap scum and declared success….again.