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Reduced Pressure Principle Backflow Preventer Troubleshooting

Symptom Probable Cause Remedy

Sudden or Rapid Spitting Drop in inlet pressure Install an in-line spring loaded check valve or pressure reducing valve upstream of backflow preventer.

Sudden increase in downstream pressure due to waterhammer from quick closing shut-off valve installed downstream. Install an in-line spring loaded check valve or pressure reducing valve downstream of backflow preventer.

Light intermittent drip Slightly fouled #1 check. Clean #1 check and/or turn check valve seal ring over or replace.

Slightly fouled relief valve seat Clean relief valve seat and/or turn relief valve seal ring over or replace.

Slightly fouled #2 check with backpressure present Clean #2 check and/or turn check valve seal ring over or replace.

Continuous discharge Fouled #1 check Clean #1 check and/or turn check valve seal ring over or replace.

Fouled relief valve seat Clean relief valve seat and/or turn relief valve seal ring over or replace.

Fouled #2 Check with backpressure present Clean #2 check and/or turn check valve seal ring over or replace.

RP TROUBLESHOOTING GUIDE

After observing water discharge from relief valve port:

1. Close #2 shut off valve. If discharge stops, the problem is a fouled second check with backpressure
present in the system.
2. If discharge continues, then with #2 shut-off still closed, open the #4 test cock full open.
If discharge stops or is reduced, the problem is a fouled first check.
3. If the discharge continues, the problem is most likely in the relief valve.

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Symptom	Probable Cause	Remedy
Sudden or Rapid Spitting	Drop in inlet pressure	Install an in-line spring loaded check valve or pressure reducing valve upstream of backflow preventer.
Sudden or Rapid Spitting	Sudden increase in downstream pressure due to waterhammer from quick closing shut-off valve installed downstream.	Install an in-line spring loaded check valve or pressure reducing valve downstream of backflow preventer.
Light intermittent drip	Slightly fouled #1 check.	Clean #1 check and/or turn check valve seal ring over or replace.
	Slightly fouled relief valve seat	Clean relief valve seat and/or turn relief valve seal ring over or replace.
	Slightly fouled #2 check with backpressure present	Clean #2 check and/or turn check valve seal ring over or replace.
Continuous discharge	Fouled #1 check	Clean #1 check and/or turn check valve seal ring over or replace.
	Fouled relief valve seat	Clean relief valve seat and/or turn relief valve seal ring over or replace.
	Fouled #2 Check with backpressure present	Clean #2 check and/or turn check valve seal ring over or replace.