In 2005 we built a house using septic sand from Preston.Several months later a subcontractor who worked on the septic told us that cheap sand was used instead of septic sand. I called Mark Preston and he told me he saw them loading the truck with septic sand. We sold our house last month and The Buyers inspector found septic sand was not used. We lost the sale. We have contacted 3 other companies . and they confirm the findings. It will cost us $24,000 to correct. Mark Preston has refused all mail sent to him. Check your septic if installed in the past 10 years. I suggest you advise your builder or contractor not to use Preston sand.