3 Things to Know about Phase Separation

What you don’t know is costing you

PetroClear filter

Brought to you by PetroClear.

Managing the day-to-day operations of a convenience store can be filled with a wide spectrum of challenges. From ordering and stocking inventory, overseeing payroll, benefits and staff schedules, addressing customer service issues and manning the cash register, there can be many competing tasks demanding an operator’s attention.

Unfortunately, one task that can get lost in the shuffle is the need to monitor and replace the fuel dispenser filters. One type of filter in particular, designed to detect phase separation, can be the very thing that keeps fuel operators in business by helping to prevent the distribution of bad gas.


Prevent Phase Separation from Tanking Your Operation

Making sure the proper checks and balances are in place is critical for early detection of phase separation. PetroClear dispenser filters slow the flow of fuel from the dispenser when the filter detects phase separation. This can be achieved at relatively low cost and by regularly maintaining filters that are specifically engineered to sense phase separation.


Phase separation happens in ethanol-blended fuels, which today constitutes nearly all of the United States’ gasoline supply. Most of what is sold is E10, and sales of E15 are growing. With more ethanol in the supply chain, incidents of phase separation are likely to increase. Breaking down what a retailer needs to know to prevent this form of fuel contamination can help prevent it from tanking the whole operation.

What is phase separation?

Phase separation is a process that occurs inside the underground storage tank when enough water mixes with ethanol-blended gasoline. This causes ethanol molecules to attach to water molecules, which results in the heavy ethanol molecules dropping to the bottom of the tank. This leaves two layers in the tank—a gasoline layer at the top and an ethanol-water “cocktail” along the bottom.

What causes phase separation?

It only takes a small amount of water to cause big problems. In a tank with 10,000 gallons of E10, just 40 gallons of water can cause phase separation. Water can creep into fuel systems through condensation caused by:

  • Humidity
  • Rain and surface water runoff during fuel transfers
  • Through pipes and vents, spill buckets and gaskets or loose fittings

Why should c-store operators take phase separation seriously?

According to a 2018 industry survey of convenience store customers, a station’s reputation plays a large role in a motorist’s decision to purchase fuel at that station. Phase separation not only destroys product in the tank, it results in untold losses in customer loyalty and subsequent profit loss. If aqueous ethanol fuel is pumped into vehicles, it can damage automotive engine components, in some cases forcing the automobile to be towed away from the fuel site. Other costs of phase separation include the loss of sales from the offending dispenser, expensive disposal of the contaminated fuel and the need to replace potentially damaged fueling system components. 

Managing water in the fuel supply is a persistent challenge for station operators. C-store operators who minimize its impact on customer satisfaction will position their brand for a competitive future.