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Pressure Cleaning

Ductile Iron Pipe Pressure Cleaning Evaluation – March 3, 2011

Scope: Evaluate the effects of pressure cleaning to internally lined Ductile Iron Pipe.

20” factory lined DIP with Permox-CTF™ Ceramic Novolac Epoxy (Coal Tar Free)

Prior to design of the test procedure, initial research provided by The National Association of Sewer Service Companies (NASSCO) and The Ductile Iron Pipe Research Association (DIPRA) led us to further consultation with the following:

KEG Technologies, Inc.
644 Church Road, Suite 3
Madison, MS. 39110
Adams Equipment Co.
1431 Lanier Road
White Plains, GA. 30678
40 24th Street, Sixth Floor
Pittsburgh, PA 15222
Stone Age Waterblast Tools
466 S. Skylane Drive
Durango CO. 81303
Dekalb County Watershed Management
1580 Roadhaven Drive
Stone Mtn. GA. 30083
NACE International
1440 South Creek Drive
Houston, TX 77804

Test Procedure: Employ a stationary high pressure water jet stream at a 45 degree angle to test specimens with the following parameters:

  • Water pressure of 3,000 psi at the nozzle.
  • Four gallons per minute delivery
  • Nozzle distance two inches from the specimen
  • Nozzle opening 0.6 mm with a 40 degree fan pattern

Before testing:
Dry film readings to be taken at the anticipated strike area for determination of any changes to the lining surface.

During testing:
Visual inspection of the lining and water jet stream for consistency during the cleaning process.

Determine film characteristics of the lining for any effects the cleaning operation may have had including, but not limited to loss of gloss, loss of film thickness due to erosion, and overall film integrity.

The purpose for this test is two-fold: (1) to determine what effects would be obtained by non-compliance with guidelines developed by NASSCO in their publication “Jetters Code of Practices – V.2,” and (2) as a worst case scenario, allowing the jetting nozzles to remain operational without forward or reverse movement within the sanitary sewer line.


  • Graco Model 800-639 pressure washer [11 hp engine, 3000 psi (207 bar) working pressure, maximum flow 4 gpm (15lpm)]
  • Electro-Physics “Microtest III” dry film thickness gauge [ S/N 014609]
  • Rigging to hold pressure nozzle firmly at two inches from test surface at the specified angle without movement
  • Water supply
  • Digital level

Test Results & Photographs:

Pipe-1 20” factory lined DIP with Permox-CTF™ Ceramic Novolac Epoxy (Coal Tar Free)

Nominal average film thickness – 57 mils. Testing by high pressure washing was interrupted every five minutes for evaluation then restarted. Total duration of test – 15 minutes (March 1, 2011)

  • Five-minute evaluation revealed no erosion of the lining or visual change.
  • Ten-minute evaluation revealed minor opening of a few lining imperfections; however these imperfections are surface related (possibly hidden air bubble from application), maximum penetration by high pressure cleaning only reveals the void at a surface pinhole with complete lining underneath.
  • Fifteen-minute evaluation (end of test). No change from ten minute evaluation.

Results after drying – no erosion, minor reduction of gloss at strike line, nominal dry film thickness 57 mils. No visual damage to lining at strike area except for the few surface pinhole breakage which is non measurable (visually, under magnification, the pinholes /air pockets/ appear to be a maximum depth of 3-5 mils). Out of the total test surface area these pockets broken by the cleaning process comprise 0.1 to 0.25% of the total area.

Pressure Cleaning Test Result Photos

Ductile Iron Pipe Cleaning Test – Stationary Nozzle

Permox-CTF™ - Pipe 1

Permox-CTF™ – Pipe 1

Permox-CTF™ - Pipe 1

Permox-CTF™ – Pipe 1