7
Dometic Vacuum Holding Tank
Operation
6.3
Make connections
1 . Fasten VHT to floor using spindles (optional) and #12x1 .5 in . wood screws (fig .
3
, p . 2) . If not
using spindles, fasten VHT to floor with #14x1 .5 in . wood screws and washers . Be sure to fasten
at least six of the eight available mounting feet at the base of the tank .
2 . Route 1 .5 in ./38 mm ID sanitation hose from toilet to VHT inlet, and from VHT outlet to the boat’s
discharge fitting(s) (see previous section for hose routing guidelines) .
3 . Route 5/8 in ./16 mm vent hose from vacuum pump discharge to vent filter or thru-hull vent fitting .
4 . Place two hose clamps on hose near each end that attaches to fittings . Use Dometic Hose
Lubricant (fig .
7
, p . 3) or liquid dishwashing soap on fitting and inside ends of hose, then twist
hose onto fitting . Make sure hose end is flush against fitting shoulder .
5 . Tighten hose clamps at ends of hose with screws positioned as shown (fig .
8
, p . 3) .
6 . With electrical power off, make electrical connections according to the Wiring Schematic shown
on the parts list provided with this unit .
Caution!
Failure to follow the procedures above may result in vacuum leaks or inefficient flushing .
7 Operation
7.1
System start-up
1 . Fill freshwater tank, then turn on inlet water supply to VacuFlush toilet .
2 . Turn on electrical power to vacuum holding tank (VHT) .
3 . For foot-pedal operated VacuFlush toilets, flush toilet for about 15 seconds to assure water starts
flowing throough vacuum pump . For electronic VacuFlush toilets, flush five times, allowing each
flush cycle to complete (when vacuum pump shuts off) before next flush . VHT unit may take up to
three minutes to recharge vacuum level between flushes .
7.2
Normal operation
VACUUM FLUSHING ACTION
Every time the VacuFlush toilet is flushed, the VHT unit pulls wastewater from the toilet to the holding
tank . The vacuum pump then runs until the proper vacuum level is achieved for the next flush .
Follow flushing instructions in VacuFlush toilet operation manual .
“FULL” TANK PROBE
When the holding tank contents activate the “full” tank probe, a signal is sent to a shutdown relay
which turns off electrical power to the toilet system to prevent the VacuFlush toilet from flushing
and overfilling the VHT . The VHT must be emptied before electrical power is restored for normal
VacuFlush toilet operation .
7.3
Holding tank pump-out operation
To assure thorough discharge of vacuum holding tank, follow these steps:
1 . Turn off electrical power to VHT at circuit breaker and water supply to VacuFlush toilet .
This prevents vacuum pump from starting during pump-out operation .
2 . For foot-pedal VacuFlush toilets with built-in pedal lock, follow instruction in toilet operation manual
to keep flush ball in toilet open for holding tank pump-out operation . For electronic VacuFlush
toilets, follow Service Mode instructions for keeping the flush ball open . For all other VacuFlush
toilets, make sure flush ball stays open to allow air into VHT unit during pump-out operation .
3 . Pump out holding tank through dockside or overboard discharge fitting .
4 . After pump-out, close flush ball in toilet and resume normal VacuFlush toilet operation .
