Food Service/Food Preparation Wastewater Discharge Information...
Frequently Asked Questions
Why are Fats, Oils, and Grease (FOG) bad for the sewer pipes?
Fats, oils, and grease (FOG) that enter the sewer system stick to
the inside of the sewer pipes and over time build up and cause blockages.
These blockages cause backups and overflows of raw sewage that can
enter homes, businesses or the environment. Consequently, this results
in contact with disease-causing organisms, environmental damage,
increased maintenance costs and higher sewer bills.
Where does FOG come from?
FOG comes from many sources and typically enters the sewer system
through kitchen sinks and dishwashers. Grease is a byproduct of
cooking and is found in a variety of things such as: meat, lard,
cooking oil, shortening, butter & margarine, food scraps, baking
goods, sauces, dairy products, etc. These products are washed down
the drain and into sewer pipes.
What can be done to help reduce FOG problems in the sewer pipes?
The only way to keep FOG out of the sewer pipes and prevent overflows
is to keep the material out of the sewer in the first place. There
are several ways to accomplish this:
- Don't pour grease down sink drains. Pour used grease into sealable
containers and dispose of in the trashcan.
- Scrape grease and food scraps into the trashcan for disposal.
- Limit use of in-sink garbage disposals. These allow the grease
laden food scraps to move further into the sewer system where
they still can cause problems.
- Dry wipe greasy cookware prior to cleaning.
- Clean and maintain commercial grease traps/interceptors frequently.
- Talk to your friends and neighbors about FOG in the sewer system
and encourage them to help keep it out of the sewer system.
What is a grease trap?
A grease trap is a typically a reservoir built into wastewater piping
a short distance from the grease producing area. Baffles in the
reservoir retain the wastewater long enough for the grease to congeal
and rise to the surface as it is separated from the wastewater and
"trapped". The grease can then be removed and disposed
What is a grease interceptor?
A grease interceptor is a vault with a minimum capacity of 500 gallons,
but typically 1000 gallons, that is usually located in close proximity
to the exterior of the building. The vault typically has two compartments
which provide enough residence time for the wastewater to cool,
congeal and rise to the surface where it accumulates. It is important
that interceptors are cleaned regularly to avoid fouling of the
How often should I have my grease trap/grease interceptor cleaned?
This is highly dependent on the type of food service operation and
volume of business. All grease interceptors should be cleaned at
least twice each year. Some establishments will find it necessary
to clean their traps/interceptors much more frequently. If grease
trap cleaning becomes too excessive customers should consider installing
a larger grease trap. We urge customers to work with their vendors
to determine the most efficient maintenance schedule. Frequent trap
cleaning reduces the grease loading and shortens cleaning time.
How do I clean my grease trap/grease interceptor?
The following procedures are recommended:
For small traps under counters:
- Bail out any water in the trap to facilitate cleaning.
- Remove the accumulated grease out of the trap. Be sure to
scrape the baffles, sides and lid.
- Deposit the grease in a watertight container and have a rendering/tallow
company pick it up.
For large underground interceptors:
You will likely need to hire a professional cleaning company with
the requisite equipment and experience.
Do not flush with hot water or use drain cleaners, enzymes,
emulsifiers or bacteria agents. These actions do not remove
grease. They only allow it to pass deeper into the sewer pipes
where it becomes more costly and difficult to remove.
What is strong waste?
Strong waste is a term applied to the relative strength of a commercial
or industrial liquid waste that is discharged into the County's
sewer system. If the discharge exceeds 250 mg/l BOD or 250 mg/l
TSS it is considered to be a strong waste. By definition, if any
commercial or industrial customer exceeds these threshold values
the customer is defined as a "strong waste customer."
Customers that discharge strong waste to the County sewer system
will have a sewer surcharge added to their sewer bill based on these
How can I reduce my surcharge?
The surcharge is based on multiple components; flow, BOD concentration
and TSS concentration. Reduce any or all of these components and
your surcharge will be reduced. Conserving water is a quick and
simple way to reduce you're the surcharge. In addition, the strength
of wastewater (BOD and TSS concentrations) can be reduced in many
ways. The easiest way is to examine your housekeeping practices
and take note of what is put down the drain. BOD and TSS surcharges
may be reduced by minimizing discharges of the following:
- milk and dairy products
- dough products
- fats, oils and grease (FOG)
- cleaning chemicals
Disposal of these types of materials into trashcans and garbage
dumpsters will help reduce your surcharge and help the Department
of Public Utilities maintain Hanover County's sewer system.
In addition, use or overuse of in-sink garbage disposals, and poor
maintenance of grease traps/interceptors can result in a high surcharge.
I have improved my housekeeping practices and feel my surcharge
is too high. Can I have my wastewater discharge re-sampled?
Yes, but there are some conditions. Each year the Department of
Public Utilities will sample businesses to determine their BOD and
TSS concentrations for the following year. Upon receiving a customer's
request, one (1) additional sample will be collected and analyzed
at the customer's expense. The results of the first and the second
test will be averaged together to determine the BOD and TSS surcharge
that will be used for the remainder of the year. However, there
is no guarantee that the second sample will be lower then the first
and therefore there is no guarantee that the surcharge will decrease.
In the event that the second sample is higher, the results will
still be averaged together and used to compute the surcharge for
the remainder of the year.