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Do-It-Yourself Septic Plans


Eco-nomic logo - link to home"Waterfront Lots and Very Tight Sites may have been

platted years ago for weekend use only. The same lot

platted today would likely have to be an acre or more"

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home on a tight waterfront site from the streetSeptic Systems for Waterfront Lots and Very Tight Sites


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Intro: The following article applies to the drawing template package sold here from 

 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 waterfront lots and very tight sites. 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.

same home from the rearThe site plan for the 3 bedroom home above sits on a 50 foot wide flat waterfront lot. The front yard has just enough room for the septic tank, pump chamber and just barely enough room for a 2 car garage and driveway. The picture was taken looking down the L shaped replacement drainfield area The pressurized transport line from the pump chamber (nearest riser) runs around the house to the right side to the main drainfield in the rear under the deck.

The photo to the left shows the rear yard and unroofed deck with beams spanning over the main drainfield. The drainfield was built back here first before the house foundation. When this drainfield quits, it will likely be abandoned in place - at least for a time. There is less than 5 feet on either side of the house so heavy equipment will not fit back here to do repairs. The replacement area in the front will have to be utilized. The construction drawings for this very tight site show how everything fits together on the site. All of the minimum setbacks are met and no waivers or relaxations of any of the rules were requested. This "Septic Approved Without Conditions" status is very important for resale, appraisal and refinancing.

plat of the waterfront lotVery Tight Sites and Waterfront Lots like the one above may have been platted years ago as small lots for weekend or casual use. The plat shown to the right is for the house above. This lot covers 6,000 sq ft. If the lot were platted today for a house on a septic system, it would likely have to be an acre or more (seven times the size we are working with.) These older lots are found in every state clustered around a lake or some other natural feature. Today's owners on the same small 50 foot wide lot may want a 4 bedroom house, a three car garage, and space for a future pool. Deciding what will or won't fit on the lot should start with the septic system not the house plans. In some soils the septic will take more space on the lot than the house.

Although local health has the authority to approve or deny your project as submitted, most health departments will be reluctant to deny your septic system on a legally existing platted lot unless the soils are impossible. However they can restrict the number of bedrooms and they can force you to build a more expensive system. The plans that we provide are examples where every possible inch of space is utilized. The septic system may not restrict your use of the very tight site as much as you may think.

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another very tight waterfront siteThere are several strategies available in most areas to help you fit everything in;

Its time to lay it out in CAD - or alternatively to get out the graph paper. Detailed site planning is next based on a site evaluation or perc test. This test will determine the best location or only location for the drainfield plus the drainfield size (in square feet.) The tank and drainfield have minimum setback distances to the other things on the site. For instance the tank can be no closer to a building than 5 feet. The drainfield can be no closer than 10 feet to a building but can be as few as 5 feet from the tank. The setback chart included here as an example is for Washington State. Your state and county rules will likely be similar but some setbacks and minimum sizes may be very different.

Drawing the rest of your site plan is like putting a jigsaw puzzle together. Property lines, driveways, the drainfield, the 100% replacement area, the house footprint (if this is known at this time,) any water wells and water lines near the septic make up the bulk of the things to show on the plan. The drainfield for the 2 bedroom house above (click to see site plan) is shown under construction in the picture below. The gravel (drainrock) type drainfield (bed design)  is being prepared by the excavator with filter fabric before final inspection, squirt testing and then backfill. The fabric keeps backfill dirt out of the drainrock.

tight site drainfield under construction

Strategy 1. Squeezing: Check the soil chart for calculating the drainfield area. If the soil type is a sand, rather than a loam, a more compact bed design as shown here to the left rather than a standard trench design can be utilized. The waterfront site directly above and left is a good example of squeezing everything into the front yard. The 100 ft setback to the lake (surface water) and the private water well near the shoreline pushed all of the septic into the front yard. This allowed only enough room in the front for all of the septic but only enough room for a single car garage with room for 2 cars outside on the driveway. Click for a close-up of the pump chamber for this the Devlin System.  Notice that the usual 2 foot space between the tank and the pump chamber has been shrunk to 6 inches and back filled with sand. 

Strategy 2. Odd Drainfield shapes can some-times fit into impossible spaces. Here the full width of this 480 sq ft L shaped bed below would not fit across the width of the lot and allow a ten foot driveway to the interior of the lot. Soil conditions called for a 48 x 10 ft bed. Because beds can be no wider than 10 ft, a small portion of the drainfield (30 sq ft) was hanging over the line. Local health was OK with the L shaped bed design shown below pushing the extra around the corner. The alternative would be to break the drainfield in half eating up more space on the lot than is available.

The picture below right shows the health inspector using a metal probe to verify the drainrock depth in the L portion of the drainfield. The grey material spiked to the wall of the excavation is a 30 mil vinyl barrier to block the tree roots from the nearby poplars from invading the drainfield, one of two standard methods of controlling tree roots in the drainfield. Without this odd drainfield shape, the 4 bedroom drainfield would be reduced to a 3 bedroom drainfield. Eco-nomic provides the septic design drawings to cover most situations you are likely to find in the business. For your special site situation you can modify our templates to make your own drawings showing whatever details you may need for your applications.

L shaped drainfield being inspected for final coverStrategy 3. Bending the rules: If you are lucky, local health inspectors will sometimes look the other way on a rule. This used to happen a lot more in the past than it does now. These days your neighbors may have been put through the ringer on their septic system. They might complain to the authorities about you or anyone else in the neighborhood getting a break on the septic rules.

Officially Requesting a Waiver of state or local septic rules is often worth a try. This was done in two cases on the Devlin layout above. Take another look at the notes in red on this plan. The drainfield set-back to the garage was reduced from 10 feet down to 6 at the building corner. This reduction was allowed as the garage is not considered to be a habitable space. The normal 5 feet between the drainfield and the replacement area has been reduced from 5 feet down to 3. Both of these changes to the rules required a written waiver application and review. If these rules were not bent a little, the house drainfield would not have met the new state minimum system size (240 GPD.)

tight site - no where to park except on the drainfieldIn impossible soils (like almost no soil over solid rock or a high water table,) you may be able to come up with something radical and mechanical that might work (see black box septic.) If you can sell the idea to the state technical board you may get permission to propose an experimental design. Each year only a handful of these experimental plans get past the committee. The state is looking for some public health benefit to allow rules to be bypassed, so think about how solving your problem might help the board solve one of theirs. Any proposal to cheaply reduce nitrogen in a septic system for instance would be looked at these days with interest.

The narrow property to the right has no space for parking that is not in the drainfield area. The author has applied through local health to the state for an experimental drive-on-drainfield for this situation. The lack or aeration under pavement is solved by air injection into the bottomless sand filter media below the drainfield. The compaction at the soil interface is reduced by the use of spread footings under the vaults made of composite decking planks. The state did not buy it as they want people to stay off the drainfield area with parking and paving. This rule is too to deeply ingrained to bend, but think of the space that would be freed.      

septic tanks and pump chambers squeezed in between the housesStrategy 4. Multiple Uses of Space: Like the drive-on-drainfield proposal above, some spaces can be used for more than one purpose. In the picture to the left, the driveway between buildings was able to be used for 2 septic tanks, one for each building and the pump chamber (closest to the camera.) The tanks are traffic bearing and they have concrete risers and cast iron gas tight lids. Each traffic bearing tank costs under $200 more than a conventional tank with plastic risers and lids. Putting traffic bearing tanks in driveways and garage aprons is often a relatively painless way to grab a little extra space on the site.

Tanks can be placed under decks at very shallow depth even with one or two feet sticking out of the ground without worry over freezing (except in the Alaskan interior.) Non solid pavers can in certain cases be placed over drainfields and used as patios.

waterfront houses - not much extra room on the site for the septic systemsOff-site drainfields can sometimes move the problem somewhere else. The L shaped drainfield featured above is across the county road from the two 2 bedroom waterfront houses that it serves. This allowed the full width of both waterfront lots to be used for parking. Our drawing package includes a suggestion for a perpetual sewage easement that would be required to guarantee access to the drainfield area for maintenance and repairs. We also suggest having a professional surveyor draw up the legal description of the easement and an attorney go over the language. Permission should always be sought from public works before crossing or using a public right-of-way. Perpetual sewage easements are easier to obtain if one party owns all the lots at the time of application or as part of the platting process. 

What Does the Drawing Package Contain? The package shows a variety of designs for the septic system for waterfront lots and very tight sites plus examples of 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, shorelines, high water marks, drainfield design, site contours, 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 as well as instructions and photos to illustrate the work

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A Septic System for Waterfront Lots and Very Tight Sites  - Last Revised: 11/11/2016

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