I'm a homeowner. I've seen some kind of an inexpensive "meter" for sale for about $15 that you place in the return air stream/system that you 'zero' when you place a new filter(s).When the resistance/negative air pressure increases to a certain spot on the meter, It lets you 'know' it's time to change the filter(s) for your central hvac system...Are these bunk or are these worth fooling with? I'm trying to use the thicker pleated filters that last longer rather than the cheap monthly filters.
Thanks in advance, Mike