I have a 30-year-old Carlin 100crd with Webster m34dj-3 pump hot water heater whose fuel lines are paralleled with a 50-year-old national boiler with Sundstrand j3bb pump. When the Carlin fires a relay shuts down the National (my idea after the oil company that installed the Carlin had problems when both fired). This has been working for over 30 years and I now realize that the three times I had problems, including once when I replaced the pump on the Carlin, the tank was refilled and that is what really cured the problem. The tank is 6 foot underground with about a 25-foot horizontal run to the boilers that are at ground level. While the Carlin got noisier and eventually could not fire, the National keeps chugging along although the pump is now noisy. I now have the Carlin running from a 5-gallon diesel can while waiting to get the tank filled and it works fine and is quiet. I wonder if the National would keep running until the tank is nearly empty but do not want to test since it is below 30 degrees outside. There is no fuel filter in the lines, I have one but do not want to install it until the main problem is fixed. A few questions: 1. Do I need a booster pump? 2. Would a two-stage pump on the Carlin solve the problem? 3. The Carlin manual says to install supply line fuel cut off solenoids tied to the burner motor of each unit. Is this necessary since it has worked so long without them? Your suggestions please.

We have had sub-zero temperatures for the last week and today when temperatures started to rise we had pipes burst. We had our plumber turn off the water until he can return tomorrow to work on the problem, but we now have no heat coming form our hot water boiler or registers. Do we need to do anything for safety to the boiler until the water is turned back on like turn off the pilot? Thanks!!!