Hydrotech Classic Series Stenner Basic Service Manual - Manual (Page 17)

16 Maintenance Basics – Tube
Excessive back pressure at the point of injection
Blockage or restriction located inside the injection fitting
portion of the check valve due to calcification or mineral
deposits.
Corrective Action
1. Insert a round shank screwdriver through injection fitting
into the pipe to locate or break up accumulated deposits.
If screwdriver can’t be inserted, drill the deposit out of
the injection fitting. Do not drill through the opposite
pipe wall.
2. Replace duckbill.
Tube Failures
Causes and Corrective Action