8-when all else fails backflow prevention

8/10/2019 8-When All Else Fails Backflow Prevention

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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


Influence of Pump Station Wet Well

Sewer Lateral Connects to Interceptor


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Common Situations


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Common Situations



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




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




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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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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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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8-when all else fails backflow prevention

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