Characterizing water-based fluids.
by Hydraulic Institute
May 10, 2019

Our commercial building has many pumps, but I am not clear on what fluids are being handled. What types of fluids are being pumped/handled?

Fluid streams within a commercial building are generally water based but sometimes include chemicals for disinfecting. The water-based fluids may be characterized as follows:

Caution Sticker
  • potable (domestic) water
  • nonpotable, clean water
  • wastewater
  • greywater
  • glycol and water mixtures

Potable (domestic) water is city or well water that has been treated and is safe for human consumption.

Nonpotable clean water contains minimal or small solids; however, it is not suitable for human consumption.

Wastewater may include household and commercial solids, large solids, stringy material, sanitary waste, plastic scraps, food waste, sticks, leaves, abrasive materials and other inorganic and organic solids. What becomes more prevalent in wastewater flows, though, are personal wipes, towels, cleaning cloths and household cleaning materials that are marketed to be discarded through the sewer system.

These materials, in addition to the stringy materials and rags, can bind to create a large mass that can lead to clogging issues in the wastewater pump and associated piping. Rotodynamic pumps designed to deal with solids and minimize clogging are referred to as solids-handling pumps.

Greywater can be water from a sink or bath that is kept separate from wastewater from toilets and sewer systems. It may also be harvested rainwater that is collected in a cistern.

Glycol and water mixtures have properties that differ from water. The viscosity is increased, the boiling point is increased and the freezing point is lowered. Glycol is typically added to hydronic systems to prevent the liquid from freezing at temperatures below the freezing point for plain water.

Propylene and ethylene glycols are typically used in commercial buildings. Most glycol manufactures recommend that the water mixed with the glycol be treated to prevent minerals commonly found in city water supplies from reacting with the glycol.

The fluid streams within buildings may contain one or more of these characteristics. The properties of these fluid streams create different considerations that need to be addressed when selecting a pump for the intended service.

The pump user should identify and communicate to the pump manufacturer the nature of the fluid for each application to ensure reliable operation.

For more information on fluids pumped in commercial buildings and pumping considerations, refer to HI’s new guidebook Pump Application Guidelines for Commercial Building Services at www.pumps.org.

Read more HI Pump FAQs by clicking here.