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Elevator hoistway drainage FAQs, large or complex system insights, and more!

Public Health updates for Plumbing & Gas Piping





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Protecting Public Health Plumbing and Gas Piping Newsletter




November 2024






General Announcements

*Permitting and plan review fee changes*

The Plumbing and Gas Piping program has recently undergone a rate study to assess the resources needed to support the inspection and plan review services offered to our customers. A revised Fee Schedule will likely be in effect beginning January 1, 2025 pending approval by both Seattle and King County councils.

In addition to the rates being revised, the actual fee structure is being simplified so that each permit type (Gas, Plumbing, Backflow, Medical Gas) will have the same rate structure and the same per-fixture cost. Instead of rates being different for 1 fixture, 2-3 fixtures, 4-6 fixtures, etc., there will be a single flat base rate followed by a set per-fixture cost that will be calculated to determine the overall permit fee. More detailed information will follow in our December newsletter.

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Plan Review Updates

*New 90 day limit for plan review responses*

A new amendment to the 2021 Seattle Plumbing Code includes a provision that would invalidate previously approved drawings if the permit applicant does not respond to a request for plan corrections or plan review invoice within 90 days of issuance or if permit fees have not been paid within 90 days of plans being approved. This amendment was created to prevent the ‘warehousing’ of approved plans in our system without payment being made for outstanding plan review fees or a permit being pulled. Exceptions will be considered on a case by case basis. Reference section 108.7 of the 2021 Seattle Plumbing Code for additional information.

*‘Large or Complex’ systems may require plan review*

When our Occupancy and Use [ https://cdn.kingcounty.gov/-/media/king-county/depts/dph/documents/health-safety/environmental-health/plumbing-gas-piping/occupancy-and-use.pdf ] document was overhauled in 2023 using input and feedback from our industry partners, a provision was added for ‘Large or Complex’ projects to be subject to plan review on a discretionary basis. There are some projects that do not necessarily meet the normal criteria for plan review but are complex or large enough that our field inspectors are not able to assess the overall system to confirm Code compliance in the field.

Below are some specific examples of projects that may fall into this category:


* Projects with more than (10) fixtures or outlets
* Large Category 3 or Category 4 medical gas or non-medical gas systems
* Commercial sanitary waste heat recovery systems
* Unusual or uncommon processes or system configurations

This provision is used discretionarily, meaning not all projects with more than 10 fixtures will be subject to plan review automatically. For example, if you are installing (4) lavatories, (4) water closets, (2) floor drains, and a drinking fountain and there is nothing else particularly odd about the project, it would still be allowed to proceed as an over-the-counter permit. If, however, you are working on a salon with (8) foot baths, (2) lavatories, and (2) water closets, that may be subject to plan review because there are inherent Code compliance and design considerations involved with foot baths regarding cross connections and drainage.

As always, when in doubt please contact us at planreviewinfo@kingcounty.gov to confirm if plan review will be required for your project prior to pulling an over-the-counter permit.

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Featured Article: Considerations for Elevator Hoistway Drainage

"By Dave Price, Assistant Chief Plumbing Inspector, Public Health - Seattle & King County"

While I don’t recall the exact year it became effective, I do recall the chaos that ensued when American Society of Mechanical Engineers (ASME) standard A17.1 began requiring a drain or sump pump in all hoistways serving elevators with Emergency Firefighter’s Operation. Plumbing engineers everywhere had questions such as “Is this real?”, “Is it being enforced?”, “What is Emergency Firefighter’s Operation?”, and “Where am I supposed to discharge this sump pump?”.

Most engineers and designers now have at least some idea of how to meet the ASME A17.1 requirements within our jurisdiction. It helps that Washington State Labor and Industries (L&I) adopted the 2019 version of the standard late last year (City of Seattle had done so previously), so finally the entire state is using the same version. One notable change in the 2019 version is that it now requires 50 gpm of drainage (3,000 GPH) per *hoistway* instead of per *elevator* – a welcome revision for designers and engineers working on large high-rise projects.

A number of amendments to the 2021 Seattle Plumbing Code (SPC) were drafted specifically to provide guidance to the industry on elevator hoistway drainage, with input from the WA State L&I Elevator group and Seattle’s Conveyance team.

Starting with the basics, drainage lines from hoistways (either pumped or gravity) must discharge *indirectly* to the building sanitary system through an approved indirect receptor. This is spelled out in ASME A17.1 and the new exception to 2021 SPC 710.4. If a pump is used, a check valve and lockable gate or ball valve must be installed on the discharge line *outside of the hoistway* to allow servicing and inspection without having to access the hoistway itself (2021 SPC 710.4). There must also be a way of keeping the air in the hoistway separate from the air outside of the hoistway to prevent smoke or other pollutants from entering the hoistway. If the hoistway is being served by a sump pump, the check valve on the pump discharge line provides this protection. If the hoistway is being gravity drained, this can be accomplished with a running trap or normally closed backwater valve (2021 SPC 803.3, Exc. 1)." See the below image for more details. "

PGP Newsletter 1

When assigning DFU loading to elevator hoistway pumped discharge lines, the intermittent use chart (SPC Table 702.2(2)) may be used (2021 SPC 710.5 Exc.), however all downstream piping must still be sized to accommodate the actual design flow rate.

We often receive questions asking if the elevator hoistway can be drained into a building’s parking garage drainage system. The answer is yes, but only if the sand interceptor or oil/water separator acting as the trap for the garage drainage system is sized to accommodate the full flow of the hoistway drainage discharging to it. "See the below image for more details."

PGP 2
Frequently Asked Questions

*Does the pumped discharge line from a hoistway sump pump need to be metallic pipe?*

Not necessarily. If the pumped discharge line is fully below the sump grate until it exits the hoistway, it may be any code compliant material. If the pumped discharge line is exposed at all within the hoistway (above the sump grate), then the line needs to be metallic. This is not a fire rating issue, it is a practical issue to prevent any falling objects from damaging the pipe.

*Is there a special type of drain that needs to be used within a hoistway?*

The drain should have a metallic strainer and drain body and preferably be of the parapet type (L-shaped strainer). That will provide some open strainer area above the bottom of the sump so that debris doesn’t accumulate on top of the entire strainer and prevent it from draining when needed.

*Am I required to use an oil-sensing pump system?*

No, but if you do it needs to continue to operate under emergency conditions if water is present in the hoistway.

*How big does my sump need to be? Is there a minimum size?*

The sump needs to be large enough to fully house the sump pump with a metal grate above it sitting flush with the bottom of the hoistway. Remember to consider space for floats and a union in the discharge line for pump removal. 18”x18”x18” was traditionally considered the minimum sump size in the SBC for hoistway sumps without a pump or drain. There is not currently a minimum prescriptive size for sumps with a drain or sump pump in them except that it needs to be large enough to accommodate the sump pump and accessories as noted above.

*Does the pump have to discharge to an oil/water separator or sand interceptor?*

In most cases no. Most newer hydraulic elevators use a bio-degradable vegetable based fluid that is not detrimental to the sewage system if accidental spillage occurs as part of a life/safety event. If you are working on an older building using hydro-carbon based hydraulic fluid, then the discharge would need to be routed to an oil/water separator or sand interceptor.

"Hopefully this article has helped answer some of your questions regarding hoistway drainage. If you have suggestions for future articles, please let us know at planreviewinfo@kingcounty.gov."

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