As previously noted in the thread, In almost all water/sewer situations, only the potable water is meter and you pay for sewer based on the metered water usage.
In some cases sewer usage and base fees are charged by the size of the sewer line (typically when the water is not metered). So if the sewer lines were replaced this could be the reason for the decrease.
If a major water leak was repaired, often the municipal utility will credit or lower the sewer portion of the bill due to the water/sewer did enter the sewer facility (instead leaked into the ground).
Finally sewer charges may have been based on an (historically high) average annual water use applied to current sewer charges. This is often the case when water is charged from one provider and sewer is charged by another provider. A credit (for over estimated sewer usage) on the sewer charges may have been applied over several sewer bills.
Regardless, appears your water sewer charges have been stable for a couple of years. If you are using @ 1500 to 3000 gallons per occupied home, than your within normal range.
Older meters do not capture (charge 100%) of water usage. A new meter will increase the water usage charges.
Sewer rates through out the US continue to increase at more rapid pace than water charges. In most urban areas, sewer cost more the water, so it cost more to flush than to fill your toilet.
Feel free to contact me for more information on your specific mhp.
We’re here to answer your water sub-metering questions.
Southern Water Management