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Free AutoCAD septic tank and on-site wastewater symbols (DWG): tanks, drain fields, mounds, sections

Septic tank and on-site wastewater: 176 ready-made AutoCAD blocks (DWG), free to download and use in your own projects, as a ZIP or one symbol at a time.

176 blocks at real size in plan and section: septic tanks of 750 to 2000 gal and 2000 to 6000 L with one or two compartments, round tanks, pump and dosing chambers, holding tanks and lift stations; aerobic units, filters, disinfection, wetlands, lagoons and grease interceptors; distribution, drop and valve boxes, manifolds, risers, ports, pumps and controls; gravel, chamber and pressure trenches, absorption and drip fields, mounds, at-grade and evapotranspiration beds, seepage pits; field layouts, reserve areas, pipes, fittings, wells, test marks, setback lines and sections.

Version 1.0 · updated 30 de outubro de 2026 · Check out what's changed

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Using AutoCAD 2017 or an earlier version? Download the 2010 format

Copyright CADXChange. Use and modify the symbols freely in your own drawings and projects, including commercial ones; credit and a link are needed only when you publish them. Please do not redistribute or resell the library. Each ZIP holds one plain DWG file in AutoCAD 2018 format and a README; no add-in needed. Provided as is, without warranty. Library terms (CXL-1.0)

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All 176 symbols

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Attributes for parts lists

Every block carries a tag you can number and invisible attributes for the schedule. A tank holds TANK_TYPE, CAPACITY_GAL, CAPACITY_L, LENGTH_MM, WIDTH_MM, COMPARTMENTS, MATERIAL and the inlet and outlet invert depths; a treatment unit holds UNIT_TYPE, SIZE, DESIGN_FLOW_L_D, DESIGN_FLOW_GPD and POWER_W; a field holds FIELD_TYPE, SIZE, TRENCH_WIDTH_MM, PIPE_DIAMETER_MM, MEDIA, LOADING_RATE_L_M2_D and AREA_M2.

How to use the library

  1. Unzip the file and open the DWG. Copy the symbols you need into your plan, or drag the blocks in from DesignCenter (ADCENTER).
  2. The blocks are drawn at real size in millimetres, 1 drawing unit = 1 mm, so a 1500 x 2500 tank is 1500 x 2500 units on the site plan. Tank sizes are typical plan sizes for the nominal capacity; makers differ, so check the data sheet of the tank you specify and change the block if needed.
  3. Tanks, boxes and treatment units are centred on their middle with the flow from left to right: the inlet pipe stub is on the left, the outlet stub on the right, both on the horizontal centre line. Trenches, beds and mounds start at the feed pipe: the origin is the start of the trench on its centre line, so you can place the block where the pipe from the distribution box arrives.
  4. Sections are drawn with the ground line at Y = 0 and everything below it at negative Y, with the insertion point on the centre line at the ground line. The marker blocks (reserve areas, setback lines and circles, test holes, no-vehicle zones) carry no product attributes; scale a setback circle uniformly to the distance your authority requires.

About the drawings

There is no standard for the symbols of septic and on-site wastewater drawings. The blocks follow the common conventions of the trade: tanks as rectangles or circles with their risers, inlet and outlet stubs and tee baffles, distribution boxes with their outlets, trenches with the perforated pipe on the centre line, mounds as nested outlines of bed, fill and toe of slope.

The blocks are our own drawings, not copies, and the library is not certified. Sizes are typical; the design rules of on-site systems, such as setback distances, loading rates and trench lengths, differ between authorities, so size and place every part to your local rules and the design of your engineer or designer.

What changed in each version

Version 1.0 · 30 de outubro de 2026

New symbols (176)

Septic tank 750 gal, 1 compartment · Septic tank 750 gal, 2 compartments · Septic tank 1000 gal, 1 compartment · Septic tank 1000 gal, 2 compartments · Septic tank 1250 gal, 1 compartment · Septic tank 1250 gal, 2 compartments · Septic tank 1500 gal, 1 compartment · Septic tank 1500 gal, 2 compartments · Septic tank 2000 gal, 1 compartment · Septic tank 2000 gal, 2 compartments · Septic tank 2000 L, 1 compartment · Septic tank 2000 L, 2 compartments · Septic tank 3000 L, 1 compartment · Septic tank 3000 L, 2 compartments · Septic tank 4000 L, 1 compartment · Septic tank 4000 L, 2 compartments · Septic tank 5000 L, 1 compartment · Septic tank 5000 L, 2 compartments · Septic tank 6000 L, 1 compartment · Septic tank 6000 L, 2 compartments · Septic tank, round, 1200 · Septic tank, round, 1500 · Septic tank, round, 1800 · Septic tank, round, 2100 · Pump chamber, 1000 x 1000 · Pump chamber, 1800 x 1200 · Pump chamber, 2400 x 1500 · Dosing tank with siphon, 1800 x 1200 · Holding tank 1000 gal · Holding tank 2000 gal · Holding tank 3000 gal · Lift station, 900 · Lift station, 1200 · Lift station, duplex, 1500 · Lift station, duplex, 1800 · Aerobic unit, 3 chambers, 3000 · Aerobic unit, 3 chambers, 4500 · Clarifier, round, 2400 · Spray filter, round, 2000 · Spray filter, round, 3000 · 136 more

Frequently asked questions

Which tank sizes are included?
Rectangular tanks of 750, 1000, 1250, 1500 and 2000 US gal and 2000, 3000, 4000, 5000 and 6000 L, each with one or two compartments, and round tanks of 1200, 1500, 1800 and 2100 mm. Holding tanks of 1000, 2000 and 3000 gal, pump chambers and lift stations come in several sizes too. The capacity and plan size are in the attributes.
Do the setback circles give the required distances?
No. The circles of radius 15000 and 30000 are drawing aids; the distance you need depends on your authority and on what is being protected. Scale the circle uniformly to the required distance, or draw your own with the setback line block.
Can I use the symbols in commercial projects?
Yes. They are free to use and modify in your own projects, including commercial ones. They are provided as is, without warranty. Please do not redistribute or resell the library; see the library terms.
Which blocks do I use for a complete system?
Start with the tank, then a distribution box or a pump chamber with a manifold, then the trenches, bed or mound, and join them with the line blocks. The three field layout blocks show a parallel, a serial and a pressure-dosed field as a starting point, and the section blocks give the details for the permit drawing.
Can I change a symbol or add attributes?
Yes. Open the DWG, edit a block with BEDIT to change it or add attributes, and save. To update drawings that already contain the block, run ATTSYNC or replace the block. Make a backup first: attribute values can be lost if ATTSYNC is used carelessly.
Where do I find a ready-made set of these symbols for AutoCAD?
AutoCAD itself ships only a small set of sample blocks, so a full symbol set has to come from a library. Download the ZIP on this page and open the DWG: every symbol is a block. Insert one with INSERT (Blocks palette, Libraries tab, then pick the DWG) or drag it from DesignCenter (ADCENTER). You can also download a single symbol on its own.