INSTALLATION, OPERATION, &
MAINTENANCE MANUAL
TITLE:
F70VP Series
Rev. B
Vacuum Relief Valve
Page 18 of 20
7.0
TROUBLESHOOTING GUIDE
Symptom
Possible Cause
Remedy
The main valve leaks
around the cap or cap
bolts.
Cap bolt(s) loose, or insufficient /
uneven bolt torque.
Retighten the cap bolts per Section 3.2.
Sealing surface on cap is
damaged.
Repair defect or replace cap.
Upper liner seal is damaged or
contaminated.
If damaged, replace with new seal(s). If
contaminated, clean and reinstall.
Air trapped in cap bolt hole(s).
Wait until leakage stops (applicable to
very recent cap reinstallation only).
The main valve leaks
through the bottom
(system) connection.
Damage to, or contamination on,
piston seat or main valve nozzle,
piston seal / sealing surface, lower
liner seal / sealing surface, or
backflow preventer check valve
seating surfaces.
Disassemble the valve, remove the
piston and liner, and examine seat(s),
seals, and sealing surfaces under
magnification. If damaged, replace with
new part(s); if contaminated, clean and
reinstall.
Dome is not loading properly
through the pilot.
Check pilot or tubing for obstructions;
clean / unplug.
The main valve does not
open.
Pilot valve not set correctly.
Check set point on pilot. Ensure correct
pressure units are being used (“psi vac”
vs “psia”).
Vacuum not maintained in pilot
bonnet or main valve dome (region
between cap and top of piston).
Ensure tube fitting in bonnet is tight.
Verify that Teflon seal is installed under
pressure adjustment screw lock nut. If
no pilot, verify tubing and connections to
main valve cap are tight.
Inlet screen or tubing to pilot is
plugged.
Clean / unplug line.
Pilot internals are blocked or
damaged.
Disassemble pilot; check / clean parts.
Main valve piston is seized.
Disassemble the valve and examine
surfaces for debris/damage. Clean or
replace parts as necessary.
The main valve does not
close, or opens above
vacuum set point.
Obstruction in main valve, pilot
valve, or tubing to main valve.
Clean / unplug. Remove any debris
between piston and liner. Provide
system filtration if necessary.
Pilot diaphragm is leaking.
Disassemble pilot valve, remove and
inspect diaphragm. Replace
diaphragm.
Backflow preventer check valves
missing or installed backwards, or
leak.
Check for proper installation and seat-
tightness.
Piston or liner seal is leaking.
Disassemble the valve, remove the
seals and examine. Clean or replace,
as necessary.
