septic dye going down a toilet How Much Septic Dye & How Much Water for a Septic Loading & Dye Test
Septic System Testing Procedure

  • SEPTIC TEST VOLUMES & DYE AMOUNTS - CONTENTS: How much septic dye & how much test water to use during a septic test. Exactly how to conduct a valid septic loading & dye test. WHERE TO BUY septic test dye powder, wax dye cakes, septic dye liquid or septic dye tablets
  • POST a QUESTION or READ FAQs about determing the correct volume of water to use for a septic loading & dye test
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Septic loading or dye test water test volume:

This article provides a table of septic loading and dye test water volumes and septic dye powder or tablets required to perform a valid septic loading and dye test.

This table includes details of the Septic Loading and Dye Test procedure for testing the function of septic systems, focused on condition of the effluent disposal section, also known as a leach field, seepage pits, drainfield or drainage field.

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TABLE OF SEPTIC TEST VOLUMES & SEPTIC DYE AMOUNTS - Table of Septic Dye Test Volumes and Septic Dye Requirements

Article Contents

CAUTION: appropriate test volumes may vary depending on the type of equipment installed. Some designs, such as dosing systems, may be approved by local officials but may be capable of only very limited fluid handling capacity per hour.

Information provided by seller, realtor, visual inspection, or neighborhood history may indicate if special limited-capacity systems are installed. The following guidelines pertain to conventional tank and absorptions systems such as tank and trench-line drainfields.

The following table is a general guide to selecting the volume of test water and the amount of septic tracer dye needed to perform a septic loading and dye test. If you're asking "how much septic dye" or "how many septic dye tablets" should I use, look here and also look at the instructions from the manufacturer of your septic dye.

Table of Septic Loading Test Volumes & Septic Dye Amount

Minimum septic dye test volume in gallons: 50 + 50 x (number of bedrooms), or 150 gallons (minimum), whichever is more. More or less, if information about system design indicates. Some inspectors use 75 gallons per bedroom for this calculation.
Desired septic dye test volume: 200 gallons. More or less, if information about system design indicates
Maximum septic dye test volume: 300 to 500 gallons. More or less, if information about system design indicates.
Number of Septic Dye Tablets to Use:

15 to 20 dye tablets for a 1200-gallon septic tank.
This may vary by manufacturer. One tablet per test 50 gallons of test volume of water run will be insufficient.

The test liquid is being diluted by the volume already present in the septic tank. Therefore a proper test needs to employ enough tablets to stain the expected volume of the tank.

10 tablets would be the bare minimum to dye a 500 gallon septic tank.

Amount of Septic Dye Powder to Use:

Minimum of one heaping tablespoon - about 1/100th of a pound or about 2/10 of an ounce by weight.
Choose red or green based on area surface conditions.

Green septic dye is fine for snowy conditions; red septic dye shows up better in grass.

Yellow Green septic dye is better for detection of effluent if there is already murky brown surface water present.

For fluorescent dyes, both dye color groups may be visible by using ultraviolet lighting, but home inspectors do not normally apply that method. The two colors will sometimes permit determination of which drain is connected to which septic tank or drywell.)

Volume of Liquid Septic Dye to Use: 1.6 oz (liquid) per 1,000 gallons of septic tank volume.

Notes to the Table of Septic Dye Test Volumes and Dye Amount

How to Determine Septic Loading Test Volume

Recommended Septic Loading: How to Determine Dye Test Water Volume, and Amount of Septic Dye

FIXTURE FLOW RATE - Estimate the test fixture flow rate during a septic test

Based on field experience, actual test measurements at 25 residences served by private well systems and observations of typical flow and pressure at residences served by municipal water supply systems, we find that 3 gpm is a reasonable estimate of flow from a single tub or un-screened sink fixture. Most private systems can deliver this volume.

Actual quantitative flow rate measurements taken at a single fixture at a single time are dangerously misleading since variations in pump pressure, pipe obstructions, valve settings, can affect flow.

If accurate quantitative measurement of flow rate is needed, and remembering that you're measuring the flow provided by the pump, pipes, valves, and fixtures, not the well flow capacity, a simple procedure is the use of a 5-gallon bucket under the test fixture, and a stopwatch. However multiple measurements may be needed to evaluate the variation in flow rate during the pump on-off cycle.

How to Set the Septic Loading or Dye Test Water Volume

Some authorities commonly test by loading the system with 50 gallons/bedroom over an hour - the likely maximum load for a typical residential system. A typical trench-type absorption field would contain this volume of water even if there were no percolation during the test period. Therefore breakout or failure at these volumes is a reasonable sign of system failure or inadequacy.

Typical septic system design handles 150 gallons/bedroom/day. [Ref. 30, Oberg, citing "Private Water Systems Handbook," produced by the US Dept. of Agriculture Cooperative Extension.]

Lockwood in our own article Septic Systems - An Engineer's View uses this same figure of 150 gallons/bedroom/day to estimate water usage in a typical residential building.

Also see Home & Outdoor Living Water Requirements for more detail.

Keith Oberg (ASHI, Binghamton NY) computes that a standard leach line for soils in central NY range from 90 lineal feet with a 3 foot wide trench and a percolation rate of 1" in 5 minutes, to 375 lineal feet of 3 foot trench with a perc rate of 60 minutes.

The gravel in a standard trench leaves approximately 38% of total volume available to contain effluent. Therefore, assuming no percolation during the test period, the water level will rise 2.35" in a 90' trench and .56" in a 375' trench. (Double these depths for more narrow gravel trenches.) These are not excessive increases in a leaching field which is typically set at least 12" below the surface with 18" depth of gravel as standard practice. It is therefore apparent that an adequate septic system should not break out when subject to this test.

Oberg applies this same test to all septic systems of all types, including sand mounds, sand filters, aeration ponds, jet aerators, drywells, cesspools, etc. If there are multiple systems the water load is split on each system and a 33% extra water load is added to account for errors in estimation of the percentage of total use.

Where to buy septic dye for septic drainfield breakout effluent indication

The first links below allow you to purchase septic dye directly from the producer.

Also see Septic Dye MSDS.

Septic System Inspection, Loading & Dye Test Articles


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