Sewer Submeter Questions & Answers

Why must we have sewer submeters with a remote encoder receiver transmitter (ERT)?

Obtaining visual submeter reads on property is time consuming, exposes meter readers to safety concerns and often requires businesses to provide escorts. Using ERT technology allows SPU to obtain submeter reads from the city right of way. SPU will still require periodic access to each submeter to obtain a visual verification read.

How do we know which ERT to purchase and whether or not to have it programmed in “hard to read” mode?

Your individual compliance plan provided by SPU will specify which ERT is required in your situation and in which programming mode it must be.

Why must all submeters be programmed to broadcast in 100 cubic feet?

100 cubic feet (CCF) is the standard unit of measure for meter reading and billing at SPU.

Can we elect not to participate in the Sewer Submeter Program?

Yes. If you choose not to meet current SPU standards, SPU will remove the sewer deduction from your account and revert your billing back to the standard method of sewer charges based on water delivered. Sewer submeters for dewatering purposes are required and you may not elect to not install a submeter for measuring groundwater discharged into the sanitary or combined sewer systems.

Can we use a meter from a manufacturer not listed under the meter compatibility list for submeter applications on the SPU website?

Yes however, the meter must meet all current SPU submeter requirements and be preapproved.

What types of meters are available on the market and how do they differ?

There are three general types of meters: mechanical, ultrasonic and electromagnetic.

Mechanical Meters have moving parts with internal obstructions and may fail due to contaminated liquid. These are designed for measuring clean, cold, potable water. Note: mechanical meters are no longer approved for use to submeter wastewater or groundwater discharge (cooling tower drains, dewatering systems, etc.)
Ultrasonic Meters use solid-state technology in a compact, totally encapsulated and weatherproof housing and have no moving parts. These meters are typically used in applications encompassing dirty liquids, chemicals and liquids with entrained particles.
Electromagnetic Meters have no moving parts and no internal obstructions. These meters accurately measure water, wastewater or fluids which are highly corrosive, very viscous or contain a moderate amount of solids.

What type of meter does SPU recommend?

Mechanical meters with a single measuring chamber work well for deducting clean, cold, potable water. Multi-register meters are rarely necessary. Ultrasonic or Electromagnetic meters are required for measuring discharge from pools, fountains, cooling towers, beverage production, and other industrial processes. Mechanical meters are not approved for any discharge submetering.

What size meter does SPU recommend?

The smallest size capable of registering your maximum flow requirements. 2” and smaller meters are typically required for all discharge meters. 3” and larger meters are much more expensive than smaller meters and are rarely necessary. Contact your equipment supplier to determine which meter will work best for your application.

Can I plumb several systems to flow through one submeter?

Yes, provided each system meets SPU requirements. Example: The supply for multiple cooling towers can be measured by one deduct meter. The overflow, drain and chemical blow-down discharge lines from multiple cooling towers can be measured by one chargeable meter.

What should I consider before purchasing a meter?

Meter size, space constraints, temperature of liquid to be measured, contaminants in the discharge, flow range (velocity) and that the meter meets all SPU requirements detailed in your individual compliance plan.

Does it matter where or how we install our submeters and ERTs?

Yes, all submeters must be installed according to the manufacturer’s recommendation.

Meters must be installed on a horizontal plane with the register face pointing up in an easily accessible area free from obstruction.
All submeters must be installed in a location where the register can be easily viewed without crawling under mechanical equipment, landscaping or up on a ladder (5ft above ground maximum height) to see the face of the meter.
All meters must be installed in such a way as to prevent air entrapment in the lines. Air in the lines will cause the meter to inaccurately record consumption and void the deduction.
Meters should be protected from freezing temperatures if installed outside.
The location of the ERT will be specified after an SPU representative visits your property and will be detailed in your individual compliance plan.

Why must an inverted p-trap be installed downstream of meters with a gravity drain?

An inverted p-trap will keep a chargeable submeter flooded with water so the meter registers accurately and prevents positive air pressure from cooling towers or other equipment from moving the meter register.

Our sewer submeters were previously approved by SPU, why are we required to make changes?

Over the years, property owners, tenants, businesses, equipment and technology will change and may no longer qualify for the same deductions using the same equipment. In some situations, submeters previously not required may now be required.

Where can we purchase sewer submeters and ERTs and who installs them?

Submeters and ERTs are both available from local plumbing suppliers. Specify that you need to meet Seattle Public Utilities requirements and refer to the submeter compatibility list. Any qualified plumber or mechanical contractor should be able to install the equipment. SPU does not maintain a list of contractors.