Download Guidelines for OWTS Installation as a PDF

The following is a summary of frequently asked questions regarding construction requirements and code changes made during Larimer County's adoption of Colorado's Regulation 43 in May 2014; 

Tank Lids and Access Risers
Access risers must be provided to grade on all tank lids, distribution boxes, and other components that require access for inspection or periodic maintenance. Lids must be watertight, and secured either with screws, bolts, chains or sufficient weight (>59 pounds). Examples of plastic and concrete lids and risers below.

Inspection Ports (10.5 B. 5)
An inspection port must be provided at the end of each chamber row in trench systems, or in the corners of a bed system. Diagram of a riser on left, showing holes drilled in portion inside chamber, observation ports at the end of a bed system, one in each corner is approved.

Distribution Box (9.8 C)
If a distribution box (d-box) is used, flow equalizers must be installed on the outlet lines to adjust flow, and the d-box must have a watertight riser to grade for access. Photo below left indicates flow equalizers on outlet, an approved riser on a d-box at right.

Piping type, Bedding, and Clean-outs
A minimum of SDR 35, no smaller than 4", with no less than 1/8" per foot fall is required for the building sewer to and effluent line from the septic tank. 1/4" per foot fall is recommended, and SCH 40 pipe is required under driveways. Bell ends of gasketed pipe must be installed on the uphill side of the pipe section. Correctly installed gasketed pipe, hub and gasket on uphill side. (Large arrow points to hub, small arrow indicates direction of slope)

Bends in piping are limited to 45 degree or sweeping 90's, two 45 degree fittings should be used to turn 90 degrees in the building sewer. Long sweep 90 on left, standard 90 on right.

A cleanout is required within 5' of the building, and for every 100' of building sewer (line before tank). Piping must be bedded in select material free of rocks or large clods prior to backfilling. The tank inlet and outlet must be backfilled and compacted to support the pipe prior to installation. Photos below show a cleanout within 5' of tank and properly bedded piping on the left, unsupported piping at the tank outlet on the right, tank must be backfilled prior to installing outlet piping.

Chamber Systems
When using chamber systems, the inlet pipe must be installed in uppermost knockout in the end cap. End caps and chambers must be installed in the correct direction to eliminate gaps, screw the end cap and first chamber together to prevent movement during backfilling. 

Chambers must be installed level, for new installations no more than 12' or four chamber rows wide. Top knockout of chamber shown with arrow below left. Four rows of chambers set level (observation ports not yet installed) on right.

Engineer Designed Systems & Final Approval (3.10 A) 
If a system requires engineer design, the design engineer must certify in writing that construction and installation of the system are in compliance with the Regulations. Prior to backfilling an engineer designed system, contact the engineer and Larimer County for inspection.

Septic Systems

Questions? Contact OWTS

(970) 498-6775