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BACKFLOW PREVENTION
Prepared by
Catherine L. Morley, P.E.
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The Surcharged Sewer Problem
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WHEN MIGHT IT BE NEEDED?
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Common Situations
Geographical Low Point
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Bottom of the Hill
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Common Situations
Geographical Low Point
Influence of Pump Station Wet Well
Sewer Lateral Connects to Interceptor
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Common Situations
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Common Situations
Geographical Low Point
Influence of Pump Station Wet Well
Sewer Lateral Connects to Interceptor Downstream of Force Main Discharge
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Downstream of Force Main Discharge
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Common Situations
Geographical Low Point
Influence of Pump Station Wet Well
Sewer Lateral Connects to Interceptor Downstream of Force Main Discharge
Downstream Interceptor Exhibits Control
Reverse Flow
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Downstream Control
0
0.2
0.4
0.6
0.8
1
1.2
0 10 20 30 40 50 60 70 80 90
Flow(
MGD)
Depth of Flow (in)
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Common Situations
Geographical Low Point
Influence of Pump Station Wet Well
Sewer Lateral Connects to Interceptor Downstream of Force Main Discharge
Downstream Interceptor Exhibits Control
Reverse Flow Amid Foundation Drain Clusters
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BACKFLOW PREVENTION OPTIONS
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Backflow Prevention Options
Floor Plug
Stand Pipe
Backwater Valve Clean Check
Overhead Sewer
External Pump-Over (EverReady)
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Floor Plug / Stand-pipe
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Floor Plug / Stand-pipe
Pros
Cheapest options
Easily accessible
Cons
Effective up to 3 head
Need good seal with floor
Cannot use basement facilities whileoperating
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Floor Plug / Stand-pipe
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Backwater Valve
Internal installation shown
Can be installed externally butneeds access chamber
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Backwater Valve
Pros
Cheapest of the valve-type options ($2,000 -$4,000)
Easily accessible Cons
All drains need to connect prior to be effective
Should not be used if foundation drainconnected
Cannot use basement facilities while operating
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Clean Check
PVC THREADED PLUG
PVC FEMALE
ADAPTER
PVC RISER PIPE*
VALVE BODY
PVC INSERT PIPE
FLAPPER ASSEMBLY
FLAPPER
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Clean Check
Pros Relatively inexpensive ($2,500 - $6,000)
Low maintenance
Easily accessible
Also a cleanout
Cons
Cannot be used if foundation drainconnected
Minimal use of facilities while operating
Roto-rooter
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Before Overhead Sewer Installation
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After Overhead Sewer Installation
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Overhead Sewer
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Overhead Sewer
Pros
Full protection
May remove foundation drain from sanitary
system
Cons
Expensive ($7,000 - $15,000)
Requires battery back-up system for poweroutages
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External Pump-Over
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External Pump-Over
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External Pump-Over
Pros
Full protection
May remove foundation drain from sanitary
system
Cons
Very Expensive ($15,000 - $20,000)
Requires auxiliary generator for poweroutages
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LIMITATIONS
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Limitations
Maintenance Rags, check valve blockages, etc.
Power Outages (overhead systems)
Requires backup power supply or cannot usefacilities
Limited Facility Use (check valve systems)
Laundry and toilet overflows COSTS
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MUNICIPAL INVOLVEMENT
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Municipal Involvement
Education Benefits
Cost Sharing
Ordinance Changes
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Overhead Sewer Conundrum
Current Basement Backups
Excess flow migrated upstream
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Benefits
Less Complaints Less Reporting to IEPA - SSOs
I/I Removal Through I/I Compliance
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Cost Sharing
Various Plans 50/50 up to max amount
Full cost up to a max amount
Higher reimbursement (or %) for FD removal
100% front with clawback
100% for at risk properties
Funding
Capital allocation Sewer surcharge
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Ordinance Changes
Any Backflow Prevention Building permit
I/I compliant
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Foundation Drain
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Ordinance Changes
Any Backflow Prevention Building permit
I/I compliant
Cost Sharing
Closing Ordinance Sump pump removal
Fines for reconnection
Teardown Policies I/I Compliance Remodeling Policies
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