Bigalt - While your freezer is plugged into a separate outlet, since it's also in the basement along with your pump it's probably on the same circuit ( both units controlled by the same circuit breaker ).
This is very true for a typical builders home. We moved to our current place in '94. The basement outlets were on 2 circuits. With separate circuits for Furnace/Air Con, water heater, sump pump (living in low area near water).
I inherited an unfinished basement with open ceilings. This allowed me to easily run lines as I fed this audio disease. Room A has dedicated 20a, 20a , 15a circuits. Room B adjacent to it has a dedicated 20a.
Now the key part for the Timeter air pump. It shares space in the area at the back of the basement with the exercise gear. My treadmill required its own 20a circuit so it got it. The pump shares this curcuit with the treadmill. One or the other is in use. Never together though. The freezer is on one of the two original shared circuits the house was wired with from the builder.
I am firm believer in the Room/Power being the biggest rocks in this hobby. No matter what gear/setups people end up with. The end result will allows be bottle necked by your Room and Power. This makes them the big rocks. Keep your gear - improve your room and power and you will continue to get improvement.
Observation
I have lived on this newer power grid/infrastructure, under developed area now since '94. I rate the power 8/10. I grew up in the city (Toronto) and moved to suburbia for a time. My city rating 4-6, and suburbia due to a newer infrastructure, single home but the same nuclear based power grid 5-6. Power conditioners were needed in the city.
Another perspective.
I had a work friend coworker who also liked audio that moved back to Hong Kong. He told me that the power demands/delivery there made Toronto seem really good. It is no surprise to me that those audiophiles in densely populated areas; on old antiquated power grids/infrastructure; that experience frequent power hits and weather related power issues, are the ones going gaga over power conditioners/grounding devices.