Have Those New Swimming Pool Main Drain Covers Reduced Your Potential Liability? How Professional Engineering Certification Improves Pool Safety Act Compliance

Greg Crowley, P.E.

Crowley Engineering LLC

• Consulting Engineering Firm

• Founded in 2003

• Licensed in 9 states

(IN, IL, OH, MI, WI, MO, CO, TX, FL)

• Focus: Facility Investigations

• Energy Audits, Solid Waste &

Recycling Studies, Municipal

Drinking Water & Wastewater

Studies, Risk Assessments,

Regulatory Compliance, Forensic

Engineering

Crowley Engineering LLC

Agenda

What is VGB Pool & Spa Safety Act?

Overview of Pool Circulation System

Where Are We Today?

What’s In Store For the Future?

Item 1

Item 2

Item 5

Item 3

Item 4

ASME A112.19.8: VGB Design Standard

• Federal Law is named after Virginia

Graeme Baker – Died in 2002 suction

entrapment event at residential spa.

• Law passed on 12/19/2007 and went

into effect 1 year later.

• Focus of VGB Act is on reducing child

drownings, suction entrapment

incidents, injuries, deaths, and public

education on importance of pool

safety.

• Affects commercial & residential pools

• Enforced by Consumer Product Safety

Commission (CPSC) & State Attorneys

General -> State/County/Local Boards

of Health.

What is the VGB Pool & Spa Safety Act

There are 5 recognized suction entrapment hazards:

• Hair entrapment

• Limb entrapment

• Body suction entrapment

• Evisceration / Disembowelment

• Mechanical entrapment

Suction Entrapment Hazards

• Design basis for pool safety act compliance per CPSC.

• Establishes testing methods for compliant drain covers.

• Provides design criteria for different types of main drain installations.

ASME A112.19.8: VGB Design Standard

• Tools are required for assembly/disassembly.

• No slotted screws.

• Corrosion resistance equal to 316 SS.

• Min. 3 threads of engagement.

• Sumps be designed for 15 insertion, tightening, removal cycles.

• Self-tapping screws and machine screws w/ inserts allowed.

• Suction fittings that attach directly to piping are allowed for PVC end connections or threaded end connections.

Fasteners

• HS hydrotherapy spa

• Used by athletes for rehab.

• Spa has single main drain in floor, and dual jet suction drains on wall (spaced less than 3 feet apart).

• New VGB covers installed by an outside contractor.

• Inspection revealed VGB covers secured w/ phillips-head self-tapping screws.

•Compliant Fasteners?

• Self-tapping screws were attached to a tacky putty adhesive placed on both sides of SS spa.

• Not possible to securely reinstall the covers after removal.

• Covers were easily removable by hand.

• Other concerns:

• No sump

• Spacing < 3 ft

•Compliant Fasteners?

• Suction fittings shall not protrude more than 2 inches from installed surface.

Grate Protrusion

• Field-Fabricated Outlets

• Venturi Outlets

• Swim-Jet Combo Fittings

• Submerged Suction Outlets

Design Criteria

Intended as single, unblockable outlets w/ flow limited to 1.5 fps or less. Design to be specified by Registered Design Professional (PE, registered Architect).

Venturi-activated outlets through indirect suction through single cover designed for debris removal.

Fittings combining suction and discharge into one housing.

Manufactured cover/grate assemblies. Those not connected directly to circulation piping must have either (a) mfr’s recommended sump below or behind cover/grate, (b) a field-built sump of the design specified by mfr of cover/grate, or (c) a sump built in accordance with Fig 2.

There are 4 specific design requirements for cover/grates:

• Sized such that a 18 inch x 23 inch body blocking element will not cause differential pressure that could cause body entrapment.

• Unblockable covers are rated by the following formula for Q, limiting volume flow rate:

Field-Fabricated Outlets – Design Criteria

Field-Fabricated Outlets - Calculations UIC Sport & Fitness Center Pool

ASME/ANSI Compliance Sizing Calculations (R1)

Design Pool Recirculation Parameters: Grate Specifications (per grate): Main Drain Parameters:

Volume Flow Rate 483 gpm Manufacturer AquaStar Dimensions: 12" x 36"

Max Pump Capacity 765 gpm Model No. RWAV12101 # of Grates in Cover: 3

Suction Pipe Diameter 8 inch Dimensions: 12" x 12"

Suction Pipe Material class A cast iron Open Area: 85.2 sq in.

Percentage Open Area: 59.2% Body Blocking Element:

Flow Rating (@ 1.3 fps): 361 gpm Dimensions: 18" x 23"

A) Q Calculation for Field-Fabricated Outlets (use smallest value of the two calculations for compliance):

1. Entrapping Force Criterion for Q

Qlim = aR*(F/(C*rho/2*aB))^0.5 where,

aB = 1.134 sq ft = largest area of openings that can be blocked by the torso specimen in the most demanding position

aR = 0.641 sq ft = area of the openings that remains unblocked

aT = 1.775 sq ft = total area of the openings in the cover

C = 2.1 = flow coefficient based on the design of the openings in the cover

F = 120 lbf = allowable lifting load that can be exerted by a conscious entrapped person.

rho = 1.94 slugs/sq ft = mass density of water

Qlim = 4.620 cu ft/s = limiting volume flow rate based on the allowable entrapping force

2073.5 gpm

2. Hair Entrapment Formula

Qlim = vmax*aO where,

vmax = 1.5 ft/s = limiting main drain velocity per ASME A112.19.8-2007

aO = 1.775 sq ft = main drain open area

Qlim = 2.663 cu ft/s = limiting volume flow rate of water flowing through main drain based on 1.5 fps velocity

= 1195.0 gpm

>> 483 gpm = pool design recirculation rate

> 765 gpm = max recirculation pump capacity

B) Sump Suction Depth Ratio (vertical distance from bottom of grate to top of suction pipe in pipe diameters)

rD = h/D where,

h = 7 inches = sump suction depth from bottom of grate to top of suction pipe

D = 7.942 inches = nominal pipe diameter based on pipe schedule and material of construction

rD = 0.8813901 < 1.5 = number of pipe diameters

• To ensure proper sizing, Q calculations should be performed.

• Compare hair entrapment formula against entrapping force formula, then apply smallest value.

• Unblockable covers are rated by the following formula for Q, limiting volume flow rate:

Represents the most common type of main drain installation. Sump depth ratio is distance from bottom of grate to the top of the suction pipe (ID) Important to take into consideration the pipe material and schedule number when calculating sump depth ratio. If 1.5 D is not available, baffles or suction diverters can be used to alter path through sump towards drain. This becomes a field-fabricated design.

Submerged Suction Outlets

Grate Specifications

• Several manufacturers of VGB grates/covers/sumps: Check out PoolSafely.org for list

• Literature sheets should specify: Model #, Size, Max Flow Rating, Open Area

• Important: Material of construction -> useful life

• Covers should have markings for ASME compliance.

• Certificate of compliance must be available, unless field-fabricated.

Grate Certificate of Compliance • VGB-compliant

grates/covers must be tested and certified by a nationally-recognized laboratory, except for field-fabricated suction outlets.

• Currently 3 federally approved testing labs:

• NSF

• UL

• IAPMO

Occasionally, a facility will have more than 2 drains. How should this be evaluated?

Multiple Main Drains

Occasionally, a pool will have more than 2 drains. How should this be evaluated?

Multiple Main Drains

Profile: • University Rec Center • Pool and Spa (no piping cross-

connect) • Pool: 123,000 gallons • Multiple features, including

whirlpool, lazy river, lap lanes, and zero-depth play area.

• Five main drains (various sizes)

• Perimeter overflow system • Piping (various sizes,

segments) • Suction piping to balance tank

and direct suction to pumps

Multiple Main Drains In a case like this, it’s imperative to develop a computational model to fully analyze the system flows

Necessary to review pump curve to determine range of system flows, especially maximum pump output

Several parameters define pump curve, including motor speed, impeller diameter, horsepower rating.

VGB grates should be rated to handle maximum pump output, while maintaining grate velocity at or below 1.5 fps, or state-mandated velocity if lower than 1.5 fps.

Pump Specs

VGB Act supports use of SVRS as back-up system to VGB-compliant grates/covers.

Many existing pools have SVRS built into system via balance tanks, surge pits, atmospheric vent pipes.

Also, several commercial products on market.

Usually, added to back-up single, blockable main drains; dual-drains spaced less than 3 feet apart; direct suction systems.

SVRS - Safety Vacuum Release Systems

• Water park features and attractions are among most challenging areas for VGB compliance:

• Lazy Rivers

• Splash Pads

• Water Slides

• Wave Action • CPSC provided guidance in July

2009 that all of these water park attractions meet the qualifications of being considered a pool, when “the user has to wade or swim through the water to reach the other side or get out.”

• Retrofits often require custom field-fabricated design for compliance.

Water Parks Water Slides

Water Parks: Field-Fabricated Designs Lazy River Sumps Splash Pad Suction

• A gray area in which there has not been clear guidance from CPSC.

• Compliance is usually determined at the state or local health department level.

• In some cases, a variance may be required.

Corner Drains

• Varying levels of compliance in each state: 50 – 90% (?)

• Frustration for facility owners/operators:

• Misinterpretation of VGB compliance rules.

• Delays in obtaining answers to compliance questions.

• Difficulty in arriving at a cost-effective compliant solution.

• Increasing adoption of VGB/ASME-related language in state codes

• Movement towards a national model code for swimming pools

• Emerging litigation for injuries and deaths at non-compliant facilities

• Growing uncertainty over suction entrapment avoidance of approved covers

Where Are We Today?

Where Are We Today?

ASME A112.19.8 provides a starting point for pool safety compliance. The rigorous approach is to apply the most conservative elements of the state/local codes and ASME standard Sometimes it’s difficult to do both. Occasionally, a request for variance is required.

Health Departments & State Codes

• Increased involvement & oversight by state, county, local health departments.

• Wider adoption of VGB / ASME-specific performance stds in state/local codes.

• Property insurers becoming involved as they come to understand the risks of non-compliance and/or improper installations.

• Closer scrutiny by federal officials of grate designs and test procedures.

• New equipment (grate/cover) designs and new SVRS technologies.

• Replacement of early-adopter VGB installations for proper compliance.

• Broader market understanding and awareness of ongoing maintenance responsibility:

• Replacement of plastic covers based on expiration date: 5, 7, 10 years. • Testing of SVRS devices for proper operation.

What’s In Store For the Future?

Questions?

Gregory D. Crowley, P.E.

Crowley Engineering LLC 2224 US Highway 41

Schererville, IN 46375

Office: (219) 322-4422 Fax: (219) 322-2277

greg@crowleyengineering.com

www.crowleyengineering.com