Some observations of this arrangement:
When I am using the pump, it will draw water from either the inside tank or the outside tank, depending on the position of the tank selector valve. It will not draw water from both tanks at the same time (since there is no fresh tandem tank water transfer line). I usually use up the inside tank first, then manually switch over to the outside tank after the inside tank is empty (using the large red-handled tank selector valve located inside the kitchen cabinet next to the fridge).
When filling the tanks from the city water connection through the tank fill valve, the tank selector valve will determine which one tank receives the water. If I want to fill both tanks, I must manually switch the valve over to the other tank.
I also noticed that there is no inside shutoff valve on the tank fill line, to close off this line in the winter. Whenever there is water in the inside tank and the tank selector valve is set to use the inside tank (as it would be for winter use), there will be water going all the way down to the tank fill valve which is located outside. This water will freeze. I will probably add a shutoff valve on this tank fill line near the water pump to prevent this.
How to Drain the Hot Water Tank
The cold water faucet for the outside shower is one of the lowest points in the cold water system. With the pump OFF, opening this faucet will drain the hot water tank. Take the shower hose off before draining (I always leave mine off anyway). To facilitate draining the hot water tank, also open the outside pressure relief valve on the tank by pulling up on the little lever (remember to put this back down after draining). This will relieve the vacuum in the tank.
How to Drain the Inside Rear Water Tank
This is similar to draining the hot water tank above. First select the inside tank with the tank selector valve (the one with the big red handle located near the pump). This allows water from the inside tank to travel to the tank fill valve. With the pump OFF, now open the tank fill valve. This will allow the water from the inside tank to travel all the way to the outside shower cold water faucet. Open this faucet and it will drain the inside tank!
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