To: Members of the Castle Rock Water Commission
From: Mark Marlowe, P.E., Director of Castle Rock Water
Roy Gallea, P.E., Engineering Manager
Matthew Hayes, Technical Engineering Manager
Title
An Ordinance Amending Castle Rock Municipal Code Section 15.10.030 to Permit the use of the IAPMO Water Demand Calculator Approach [Castle Rock Service Area]
Town Council Agenda Date: September 3, 2024
Body
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Executive Summary
The purpose of this memorandum is to request Town Council's approval of an Ordinance (Attachment A) revising the Town Code to use the IAPMO Water Demand Calculator for service line sizing. The Town is working to require 0.8 gallons per flush (gpf) toilets, but the Plumbing Manufacturers International had concerns about the impact on water quality and solids removal due to the reduced water use of these toilets. The Town contracted Dewberry Engineers to evaluate the use of the Water Demand Calculator to reduce the internal plumbing sizes to reduce the possible water age within the internal plumbing. They also evaluated the potential for water quality and solids removal with the 0.8 gpf toilets. Based on typical residential water demands, water quality, and solids removal are not a concern. CR Water would like to revise the Town Code to reference the IAPMO Water Demand Calculator.
Notification and Outreach Efforts
CR Water has presented the plumbing code analysis and proposed code changes at the June, July, and August EDC Water Subcommittee meetings to members of the development community.
Discussion
CR Water has been promoting the use of 0.8 Gallon Per Flush (gpf) toilets for conservation. CR Water planning on requiring the use of the 0.8 gpf toilets in new residential construction. The Plumbing Manufacturers International (PMI) organization contracted the Town with concerns about the use of the 0.8 gpf toilets. Their concerns include potential impacts on water quality and impacts on sanitary lateral lines.
PMI's water quality concerns are related to the potential development of Legionella within the customer's supply-side plumbing. Legionella is a bacteria that causes Legionnaires’ disease and Pontiac fever. It occurs naturally in freshwater environments. If conditions are ideal, it can grow in water distribution systems. It is transmitted by breathing in mist or swallowing water into the lungs. Older people and those with specific health issues are at higher risk of getting sick. Most healthy people exposed to Legionella do not get sick.
Water age is the main concern about Legionella growth in the distribution system. It can grow to dangerous levels in weeks under ideal conditions. The ideal temperature range for development is 85 to 110 degrees Fahrenheit. The Town contracted with Dewberry Engineers to perform an analysis on the impact of the use of the 0.8 gpf toilet and possible plumbing code changes that can reduce the risks. They compared the use of the IAPMO Water Demand Calculator to the Town's current approach under the International Plumbing Code with ten typical residential homes. Their analysis determined that the risk for Legionella development within the home's internal plumbing is low. A typical single person uses enough water each day to turn over the water within their plumbing twice a day. The water heater has the highest potential risk for Legionella development. If a typical home was installed with a 75 gallon water heater, that volume would be turned over every seven days. The typical water heater is set between 110 and 130 degrees Fahrenheit, which is high enough to inhibit its growth.
PMI also indicated that there may be concerns with solids transport in sewer laterals. The plumbing code recommends a minimum velocity of 2 Feet Per Second (fps) to maintain a clean pipe. For a 0.8 gpf toilet, the minimum required slope would be 2% to maintain the 2 fps velocity for solids transport. Additionally, higher-use fixtures within the home like shower and clothes washers will help flush solids through the internal plumbing.
The Town Code will be amended to reference the use of the IAPMO Water Demand Calculator for sizing water service lines.
Budget Impact
There are no costs associated with this code revision.
Staff Recommendation
Staff recommends approval of the Municipal Code revision for the use of the IAPMO Water Demand Calculator for residential service line sizing.
Proposed Motion
“I move to recommend to Town Council approval of the Resolution as presented”
Attachments
Attachment A: Ordinance