Re: Toilet Gurgles when shower drains
Posted by Dale's Plumbing Service on November 23, 1999 at 18:47:51:
In response to Re: Toilet Gurgles when shower drains
: My house is four years old. Six months after it was built, a second septic system was installed because the original was inadequate. I have used this newer system exclusively since then. The newer system has a pump which pumps sewage uphill to the second drainfield. Until recently, it has functioned without any sign of trouble. Recently, our toilets have begun to gurgle occasionally for less than a second at a time. The water level in the bowl does not seem to rise when this happens. It happens sometimes when taking a shower. Is this a cause for concern? Do I need to have my septic tank pumped out?

John, hope this helps.

Septic Tank Pumping Guide

Find Here: When should septic tanks (onsite sewage disposal system holding tanks) be pumped? Why? What causes failures?
Links to more in-depth information.
Having surveyed and collected septic system design and testing information from many U.S. states and Canadian Provinces, I
think that information provided by the Penn State College of Agriculture - Cooperative Extension is clear and representative of
expert thinking on this topic. For clarity and content I've made minor edits to the original material.

The most common domestic wastewater treatment system used in rural areas is the septic tank-soil absorption system. The
septic tank removes settleable and floatable solids from the waste water. 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. In addition to removing solids, the septic tank also 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 in the tank. This allows the
heavier solids to settle as sludge and the lighter particles to form scum at the top. To accomplish this, wastewater should be held
in the tank for at least 24 hours. Up to 50 percent of the solids retained in the tank decompose; the remainder accumulate in the
tank. Biological and chemical additives are not needed to aid or accelerate decomposition.

As the system is used, sludge continues to accumulate in 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 point, sewage has less time
to settle before leaving the tank and more solids escape into the absorption area. If too much sludge accumulates, no settling
occurs before the sewage flows to the soil absorption field. Infiltration of sludge into the soil absorption field can cause system
failure. To prevent this, the tank must be pumped periodically. The material pumped is known as septage. This figure shows a
tank in cross-section, but you don't need to look at it to understand the text below. For more septic system illustrations see
Septic System Illustrations.

The frequency of pumping depends on several factors:

1.capacity of the septic tank
2.volume of wastewater (related to size of household)
3.amount of solids in wastewater (e.g. garbage disposals produce more solids)

Table I lists estimated pumping frequency according to septic tank capacity and household size. The frequencies were
calculated to provide a minimum of 24 hours of wastewater retention assuming 50 percent digestion of the retained solids.

TABLE 1 Estimated septic tank pumping frequencies in years
(for year-round residences)

Tank Household size (number of people)
size 1 2 3 4 5 6 7 8 9 10
---------------Years between pumping--------------
500* 5.8 2.6 1.5 1.0 0.7 0.4 0.3 0.2 0.1 -
750* 9.1 4.2 2.6 1.8 1.3 1.0 0.7 0.6 0.4 0.3
900 11.0 5.2 3.3 2.3 1.7 1.3 1.0 0.8 0.7 0.5
1000 12.4 5.9 3.7 2.6 2.0 1.5 1.2 1.0 0.8 0.7
1250 15.6 7.5 4.8 3.4 2.6 2.0 1.7 1.4 1.2 1.0
1500 18.9 9.1 5.9 4.2 3.3 2.6 2.1 1.8 1.5 1.3
1750 22.1 10.7 6.9 5.0 3.9 3.1 2.6 2.2 1.9 1.6
2000 25.4 12.4 8.0 5.9 4.5 3.7 3.1 2.6 2.2 2.0
2250 28.6 14.0 9.1 6.7 5.2 4.2 3.5 3.0 2.6 2.3
2500 3E.9 15.6 10.2 7.5 5.9 4.8 4.0 3.5 3.0 2.6

* Below the minimum size allowed in Pennsylvania and other jurisdictions

Note: More frequent pumping is needed if a garbage disposal is used. Generally the indicated frequency will vary with the
volume of solids (+20% for high volume, -20% for low volume).

Under current Pennsylvania law a 900 gallon septic tank is the minimum size that must be used for a home with three bedrooms
or less. If six people reside in a three-bedroom house, the tank should be pumped every 1.3 years. If the same system serves a
family of two, the tank would be ready for pumping every 5.2 years. Systems installed before the current rules and regulations
were implemented may need to be pumped more often, perhaps every year or less.

As indicated in the footnote to Table 1, garbage disposers will increase the frequency of pumping. For example, if this same
three bedroom house with six residents had a garbage disposal and was generally producing a higher 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 just moved into a home, you may not know the size of the tank. In this case, you should have the tank pumped and
inspected. The company pumping the tank will tell you its size, age, and condition.

Septic tanks will not fail immediately if they are not pumped. However, an un-maintained septic tank is no longer protecting the
soil absorption field from solids. Continued neglect may result in system failure and even replacement of the soil absorption field.
In some cases, site limitations may make replacement of the absorption field impossible. If system replacement is the only
option, contact your local Sewage Enforcement Officer (SEO) or municipal sanitarian or health department since a permit for
the new system will be required.

More explanation: In order for a tank to function properly, adequate liquid volume must be maintained to allow for sufficient
"settling time" which permits solids to either settle out as sludge or join the floating-scum layer at the top of the tank. Baffles in
the tank prevent the floating scum from leaving the tank, an event which would lead to rapid failure of the absorption system.
When pumping is too infrequent, even if the tank is not totally clogged with solids, the reduced liquid volume in the tank cuts
settlement time and forces small floating solids out to the absorption system, shortening its life.

Cleaning Septic Tanks

Septic tank pump and haul contractors can clean your tank. It is a good idea to supervise cleaning to assure that it is 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 is usually done by alternately pumping liquid from the tank and re-injecting it into the bottom of the
tank. The septic tank should be pumped through the large central manhole, not the baffle inspection ports. Pumping a tank
through the baffle inspection ports can damage the baffles, resulting in a destroyed leach field.

The use of additives in septic tanks to reduce the sludge volume or substitute for pumping is not recommended. In fact, relying
on additives rather than conventional tank pumping may result in failure of the septic system. Septic additives are illegal in many

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 human in
a matter of minutes. When working on a tank be sure the area is well ventilated and that someone is standing nearby. Never
go into a septic tank to retrieve someone who has fallen in and was overcome by toxic gases without a self-contained breathing
apparatus (SCBA). if a SCBA is not available, call for emergency services and put a fan at the top of the tank to blow in fresh

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, so it can be easily identified.


The septic tank is only one part of an on-site wastewater system. It is designed to remove solids prior to the effluent entering the
soil absorption field, provide for the digestion of a portion of those solids, and store the remaining solids. Biological and
chemical additives are not needed to aid or accelerate decomposition. Garbage grinders impose an additional solids load on the
system. Solids must be removed periodically to prevent them from entering the soil absorption field. For a properly designed
septic system, the tank should be inspected and pumped every 1 to 5 years.

More Information

Other Penn State Fact Sheets relating to domestic wastewater treatment systems include

SW-161, Septic System Failure: Diagnosis and Treatment
SW-162, The Soil Media and the Percolation Test
SW-l64, Mound Systems for Wastewater Treatment
SW-165, Septic Tank-Soil Absorption Systems
Document Source: Agricultural Fact Sheet #SW-161 "Septic Tank Pumping," by Paul D. Robillard and Kelli S. Martin.
Penn State College of Agriculture - Cooperative Extension, edited and annotated by Dan Friedman
Thanks: to Bob Mackey for proofreading the original source material.
The Septic Information Website includes links to information, contractors, consultants
The Home Inspection / Home Construction Page
Contact Dan Friedman, website Author

Updated 10/27/99 Created 12/22/95 File: tankpump.html
Copyright 1999 1998 1997 1996 1995 Web page content & design by American micro Publish

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