A Septic System for Larger Rural Homes

 

 

 

 

 

The following article applies to the drawing template package sold here from eco-nomic.com. 

 The drawing templates are in both standard PDF and CAD (What is a CAD Drawing?) These drawings will enable you to prepare a set of construction drawings of your project for your property. Before beginning construction, every homeowner, excavator or designer in the septic industry must hand in clear, proper scale drawings to get approval to build a septic system for larger rural homes. Important; In most areas a homeowner can prepare drawings and build his or her septic system. State and local laws tell you if you can do this yourself or if you must hire an expert. Read this disclaimer before getting started. If you are unclear about your rules, call your county or parish health department and ask for the rules in your area.

Larger homes in the country can be old converted farm houses or new construction. A Home built years ago may have a primitive gravity type septic system built when much less water was used in the home. Some old gravity systems are are still working in spite of years of limited maintenance. Lot sizes are usually an acre to five acres or more. Municipal water is seldom available. An individual water well or a two-party well is the usual water source.

When older buildings are converted to modern uses many homeowners forget to upgrade the old septic system to match the new layout. The septic system must take into account modern fixtures, habits and lifestyles. Farm houses and villages form the bulk of rural systems. However many of the new larger rural homes are for urban families or potential retirees attempting to escape the hustle and bustle of city life. Although some bedrooms may remain empty much of the time, occasional large gatherings are likely. Especially with young families the septic system must be shown to be up to the job. The septic system should be part of the overall renovation budget to avoid an emergency repair after most of the money on upgrading the home has been spent.

The following topics should be addressed for renovated older larger rural homes and new construction outside of areas covered by municipal services.

How to Get Your Plans Approved:  Whether to justify increased fees or to support the goals of "growth management" new harsh septic and planning rules are becoming widespread in areas with almost any growth. Building a septic system for larger rural homes in the country is a lot harder and more expensive than it used to be. Getting your plans approved may take several trips to the planning, building and health departments. The rules must be met or you don't build.

New rules are requiring larger drainfield areas (tougher loading rates,) larger lot sizes and deeper soil under the drainfield. Some rules can even make it impossible to build on some lots.

One example is the trend to increasing the setback between a water well and surface water (a lake or creek) which can prevent placement of the well and the septic both on the same small waterfront lot. By appearing to only address the well setback, these laws can be passed without people understanding the severe restrictions they may place on those wanting to build. Being already in their country home, your neighbors may actually agree with new restrictions. They may feel that keeping you from building will preserve the "rural character" of the area.   

It is usually possible to find a way to build on most lots, however restricted by rules. You just have to be positive and patient with your local officials. You also must show clearly in your scale drawings what you plan to build. If you hit a brick wall at the county courthouse, you may need the services of a licensed septic designer or a professional engineer even for a simple rural home. Look for someone with sufficient experience (I would say minimum ten good years in the business) to work around the rule for you or alternatively to take your grievance to the local health board or even to a state level review committee.

Easements: When planning your property, be aware of electric utility, irrigation and other easements. Several easements can occur on rural lots. Almost all septic regulations require that drainfields and tanks be set back not only from property lines but also lines of easement. Power or irrigation companies usually police their easements and may seek removal of the offending tank if discovered inside or straddling one of their easements. Also for safety before performing any excavation call for a locate of all underground utilities.   

Sewage load and How to Calculate: Although standards vary a little from state to state and country to country the number of bedrooms usually determines tank and drainfield size not the number of bathrooms or fixtures. In most areas a bedroom holds two people. Since the 1950's the public health community has accepted that each person needs 60 gallons of water a day to handle the sanitary needs (drinking, bathing, toilet flushing, cooking, clothes and dish washing.) Therefore if two people occupy each bedroom (a reasonable assumption for a full house,) this requires 120 GPD (gallons per day) for each bedroom. Therefore a three bedroom house uses 360 GPD, a four bedroom 480 GPD and a five bedroom 600 GPD and so-on.

Tank Sizes: The septic tank and pump chamber sizes (if a pressurized septic system is needed) will depend on the sewage load calculated above according to the daily flow. In most areas a 1000 gal tank is the standard for three bedrooms 360 GPD or sometimes four bedrooms 480 GPD. The rule of thumb for septic tank sizing is 2 x GPD for good anaerobic digestion. Smaller tanks will yield more carryover of oils and grease to the drainfield plus higher BOD (a measure of waste strength.)

Your local health department has determined minimum septic tank sizes and these rules must be followed. A reasonable standard would be a 1000 gallon tank for up to 3 or 4 bedrooms with 240 gallons more for each bedroom thereafter. With a larger home say 5 bedrooms, the tank size could be 1250 gal or larger for some local health rules. If the largest tank available in your area is 1250 gal, then two 1000 gal tanks plumbed one after the other can be substituted for a larger single tank to make up the required minimum tank volume. Alternatively with larger homes on one level you could design two separate systems serving separate parts of the house. You may have to negotiate this arrangement with local health and they may charge fees on each system. Fixture flow would apply.

Pump chambers when required by site conditions have space inside for generally 3 things; 1. Emergency space at the top of the tank for emergency storage during a power failure. A municipal water system will continue to deliver water to the house during a power failure. Conservative areas will require up to a full day of storage for emergencies. This should not be a problem with individual wells because power failures also stop the well pump. 2. Dosing Volume: The system is pre-set to pump to the drainfield between on and off water levels. Float settings activate the pump usually 4 to 10 inches of pumping height in the tank depending on soil texture and bedrooms. 3. The pumps are water cooled and usually the bottom 24 inches in the pump chamber in the case of turbines or 12 inches for centrifugal pumps is dedicated for only this purpose and is never included in any pumping calculations. Most residential chambers are between 750 gal and 1500 gal or larger depending more and more on arbitrary state regulations rather than the good thoughts or work of qualified designers.   

Water Supply, building footings and Other Related Excavation: On small lots when space is tight utility location is often obvious. Not so on larger rural lots. On any lot over an acre building things in the wrong place can cost you plenty to fix or annoy you every day. Deciding on the location of the well, the power tap from the perimeter of the property, the house footings, the future or existing shop, the septic tanks and drainfield, driveways, parking and the utility lines can be overwhelming. Harder still without a scale drawing showing everything.

The septic designer or you, the owner acting as the designer is usually the first one with a shovel in the ground. 

Excavators Must Get it Right the First Time: Probably placement of the house is the most important decision for the homeowners. They should listen to the experts and not get stuck on a single location until the septic site evaluation is complete. Included in the septic discussion at a minimum is the well location and power trench locations. The septic designer should be called before any excavation begins and that includes flattening an area for the house. For instance the well driller may naturally chose the most level area for the well because it is easier to drill there. This will sterilize a 100 foot circle for building the drainfield. The best soil on lots with healthy side slopes is usually in these level pockets. Giving it up to the well could easily double the cost of the septic system. Forcing the drainfield into areas un-natural to logical drainage patterns and good soil often happens in builder driven projects. I worked on a project where crossed wires on a simple house location quadrupled the cost of the septic system for the builder.

Layout Choices: The view from the living room is often the key to a great house location. Whatever the homeowners want of their new place, they must understand why the septic may cost more or less depending on home placement. The water well must be connected to power as must the house main panel. Water and power can often share the same trench so put the well in between the house panel and the nearest power pole or approved point of power connection. The septic tanks and drainfield should be downslope from the house for gravity systems. Pressure systems are much more flexible for drainfield location. The spot for a future shop and if it will have plumbing should be decided now. Driveways, future possible pools and accessory buildings should be considered before beginning any excavation. All these things should be shown on the drawings for the county health septic permit application anyway. Remember most septic components are now built shallower than in the old days - by law. Shallow lines under driveways for instance are protected with sleeves such as lengths of recycled well casing. The drainfield replacement area should be protected and not be used for parking of any vehicle larger than a lawnmower.  

Water Softeners and their Effect On Septic Systems: The high concentration of sodium in the discharge from water softeners does not harm the bacteria in the septic tank. However salt water is heavier than sewage and the sewer inflow containing salt water plunges to the bottom of the tank disturbing the normal still environment of the tank by stirring up the sludge. Larger tanks and drainfields are a way to mitigate this problem but a very costly fix.  

No Garbage Grinders Allowed Either: These sometimes very handy devices have no place connected to a septic system. Pulverized vegetables have the same density as water and will flow through the baffles without adequate reduction of sewage strength. It is recommended to use composting to eliminate organic kitchen waste in larger rural homes or increase the size of your drainfield by one-and-a-half times.

Discharge the Washing Machine Into a Separate Drain Avoiding the Septic Tank: According to some state laws, water discharged from washing machines is considered to have the same strength as sewage. After all it contains the same bacteria in lesser amounts. In these states and counties, washing machine grey water must flow through a septic tank before it discharges into a drainfield. 

In some areas discharging wash water on the surface of the ground is legal. However a fully underground drainfield for the washing machine is safer. Dogs and children are attracted to any flowing water. Viruses and bacteria can come into the home from this source so if you are discharging a washing machine outside of the septic tank, use a small underground drainfield to get rid of this wastewater. This small drainfield follows the same rules of depth and quality of materials as the regular drainfield. In short, running wash water through the septic tank along with the rest of the sewage from the house is the normal approach and should not be considered a problem for a properly sized septic system.   

What Does the Drawing Package Contain? The package shows a variety of designs for septic systems for the larger rural homes plus examples for several sites of this type. They show you how to prepare the drawings you will need for your project. Learn how to show such things as water well placement, building location, drainfield design, landscaping, construction and pipe details and all the other notes and instructions required to fully describe your project. The package contains both PDF and editable DXF drawings. 

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