Septic Tank Pumping
Paul D. Robillard Assistant Professor of Agricultural Engineering
Kelli S. Martin Sr. analysis Technologist of Agricultural Engineering
The most common domestic wastewater
treatment system utilized in rural areas is the
septic tank-soil absorption system. The septic
tank removes settleable and floatable solids from the
wastewater. The soil absorption field then filters and
treats the clarified septic tank effluent and distributes it
through the soil. Removing the solids from the
wastewater protects the soil absorption system from
clogging and failure. additionally to removing solids
the septic tank conjointly promotes biological digestion of a
portion of the solids and stores the remaining
undigested portion.
The first stage of the treatment system the septic
tank removes solids by holding wastewater within the
tank. this enables the heavier solids to settle as sludge
and the lighter particles to create scum at the top. To
accomplish this wastewater ought to be held within the tank
for at least twenty four hours. Up to fifty % of the solids
retained within the tank decompose the rest
accumulate in the tank. Biological and chemical
additives are not required to assist or accelerate
decomposition.
As the system is used sludge continues to
accumulate within the bottom of the septic tank. Properly
designed tanks have enough space for up to three years
safe accumulation of sludge. When the sludge level
increases beyond this time sewage has less time to
settle before leaving the tank and more solids escape
into the absorption area. If an excessive amount of sludge
accumulates no settling occurs before the sewage
flows to the soil absorption field. Infiltration of sludge
into the soil absorption field will cause system failure.
To prevent this the tank must be pumped periodically.
The material pumped is thought as septage. Figure 1
shows a cross-section of a septic tank.
Figure 1. Cross-Section of Septic Tank
F-161
The frequency of pumping depends on many
factors:
l capacity of septic tank
l Volume of wastewater (related to size of
household)
l quantity of solids in wastewater (i.e. garbage
disposals produce more solids)
Table one lists estimated pumping frequency
according to septic tank capacity and household size.
The frequencies were calculated to provide a minimum
of twenty four hours of wastewater retention assuming 50
percent digestion of the retained solids.
Under current Pennsylvania law a 900 gallon
septic tank is that the minimum size that must be used for a
home with 3 bedrooms or less. If six folks reside
in a three-bedroom house the tank should be pumped
every 1.3 years. If an equivalent system serves a family of
two the tank would be prepared for pumping each 5.2
years. Systems installed before this rules and
regulations were implemented may need to be pumped
more often perhaps every year or less As indicated in
the footnote to Table one garbage grinders can increase
the frequency of pumping. for instance if this same
three bedroom house with six residents had a garbage
disposal and was usually manufacturing the next volume
of wastewater the pumping frequency would be
calculated as follows:
1.3 years – [(0.2) x 1.3 years] = 1.0 year
If you have got simply moved into a home youll not
know the scale of the tank. during this case you should
have the tank pumped and inspected. the corporate
pumping the tank will tell you its size age and
condition.
Septic tanks will not fail immediately if theyre
not pumped. However an unmaintained septic tank is
no longer protecting the soil absorption field from
solids. Continued neglect might end in system failure
and even replacement of the soil absorption field. In
some cases site limitations might build replacement of
the absorption field impossible. If system replacement
is the only choice contact your native Sewage
Enforcement Officer (SEO) since a permit for the new
system are needed.
*Below the minimum size allowed in Pennsylvania.
NOTE: a lot of frequent pumping needed if a garbage disposal is employed. Generally the indicated
frequency will vary with the volume of solids (+20% for top volume -20% for low volume).
Cleaning Tank
Septic tank pumping and haul contractors will clean
your tank. it is an honest plan to supervise cleaning to
ensure that its done properly. To extract all the
material from the tank the scum layer must be broken
up and the sludge layer mixed with the liquid portion of
the tank. this can be usually done by alternately pumping
liquid from the tank and reinjecting it into all-time low
of the tank. The septic tank ought to be pumped through
the large central manhole not the baffle inspection
ports. Pumping a tank through the baffle inspection
ports can injury the baffles.
The use of additives in septic tanks to reduce the
sludge volume or substitute for pumping is not
recommended. In fact counting on additives instead of
conventional tank pumping may lead to failure of the
septic system.
Before closing the tank check the condition of the
baffles. If they are missing or deteriorated replace
them with appropriate sanitary tee baffles. It should
never be necessary to enter a septic tank. Any work to
replace the baffles or repair the tank should be done
from the outside. Decomposing wastes in the septic
tank produce toxic gases which can kill a personalitys in a very
matter of minutes. When functioning on a tank be sure the
area is well ventilated and that someone is standing
nearby. Never go into a septic tank to retrieve somebody
who has fallen in and was overcome by toxic gases
without a self-contained respiration equipment (SCBA).
If a SCBA is not accessible incorporate emergency services
and put an addict at the highest of the tank to blow in contemporary air.
To facilitate future cleaning and inspection install
risers from the central manhole and inspection ports to
the surface before burying the tank. also mark the
location of the tank thus it may be simply identified.
Summary
The septic tank is only one a part of an on-site
wastewater system. its designed to remove solids
prior to the effluent entering the soil absorption field
provide for the digestion of a little How To Find A Septic Tank of these solids
and store the remaining solids. Biological and
chemical additives arent required to assist or accelerate
decomposition. Garbage grinders impose a further
solids load on the system. Septic Tank Pumping Solids must be removed
periodically to forestall them from entering the soil
absorption field. For a properly designed septic tank
the tank ought to be inspected and pumped each 1 to five
years.