Figure: G450 Water System Components, from GV-GER-7690, Figure 3.

Eddie Sez:

The water purge system is easier on the newer Gulfstreams (G450/550) but you have to unlearn a few things from the G-IV/V to make it work correctly. In the older Gulfstreams we wanted to force water up out of the faucets to ensure the lines were empty, in the newer aircraft we allow air to flow into the faucets so the system can drain the water down the system out the drains.

The Gulfstream video, linked below, and the G450 Operating Manual hint that you can do a "partial purge" whereby you purge everything except the conformal water tank. But the only use for this procedure is if you apply power to the conformal water tank. In other words, the "partial purge" is useless!

How do you make this process as easy as possible? We have taken to dispatching with six gallons of potable water in gallon containers which we give to the FBO to keep warm overnight. We also fly with a sturdy cooler to store all our freezables on the aircraft. (If they freeze and burst, the leakage is kept inside the cooler.) We then do a complete system purge anytime the temperature is below freezing and then add our own water the next day. It is a little more trouble but it is less trouble than troubleshooting a bursted pipe somewhere underneath the floor or waiting in line for the FBO's water truck. (Plus we can say our aircraft's water system has never had anything in it but spring water.)

What follows comes from the references shown below. Where I think it helpful, I've added my own comments in blue.


When to Purge:

Figure: Water Tank Drain Determination, from G450 Aircraft Operating Manual §07-01-20, Table 1.


How to Purge — General

Figure: Touch Screen Purge Button, from Gulfstream Video.

[G450 MOL-11-0007] The water system on the aircraft features a gravity purge system, which may be activated in the air or on the ground. For aircraft equipped with galley touch screens, the purge function is located on the water system screen along with on-screen instructions. The purge process is the same for both touch screen and switch panel-equipped aircraft.


In Air Purge

Figure: Touch Screen Purge Button, from Gulfstream Video.

Begin this process at least 20 minutes prior to landing.

[G450 MOL-11-0007] Press and hold the system purge switch on the galley switch panel for 3 seconds. The supply/drain/purge valve (V2) will move to the system purge position and allow the water tank to empty. When the tank is empty, the V2 valve will return to the supply position and remain there until landing. Upon landing, the V2 valve will move to the drain position and all system valves will open to allow all supply and drain lines to empty.

Continue to Both

Ground Purge

This process will take at least 20 minutes.

[G450 MOL-11-0007] Press and hold the system purge switch on the galley switch panel for 3 seconds. The supply/drain/purge valve (V2) will move to the system purge position and allow the water tank to empty. When the tank is empty, the system will pause for up to 60 seconds. The V2 valve will then move to the drain position and all system valves will open to allow the supply and drain lines to empty.

Continue to Both


Both

Photo: Purge Screen "Are you sure?" from Eddie's aircraft.

The conformal water tank requires 7 to 15 minutes to drain from full to empty.

[G450 MOL-11-0007]

  • From this point on the purge procedures are the same for either method. Water will drain from the aft drain mast and the two forward drain ports. As a point of reference, the forward most drain port is for the drain lines and the aft drain port is for the supply lines. Some water from both supply and drain lines may exit from the aft drain mast. As the water drains and pressure is released from the supply lines, all vented cartridges will open, allowing air into the system and water out. These include the forward crew lavatory faucet (fold-up style sinks only), aft galley manual coffee maker fill valves, and toilet rinse valves.
  • CAUTION: DO NOT REMOVE POWER TO THE AIRCRAFT OR GALLEY MASTER BEFORE THE PURGE CYCLE IS COMPLETE. DOING SO MAY CAUSE WATER TO REMAIN IN THE SYSTEM, WHICH MAY CAUSE DAMAGE DUE TO FREEZING.

  • If the purge cycle is interrupted at any time prior to its completion, the cycle must be started again and allowed to run to its end to ensure that no water remains in the system. Do not turn the water system back on after the purge is completed, doing so will reset the supply and drain valves to the closed position trapping the remaining water in the system. If this occurs, the purge function must be run again.

Completing the Purge

[G450 MOL-11-0007]


Retaining Potable Water During Freezing Conditions

[G450 MOL-11-0007] If so desired, the water in the conformal water tank may be saved if power is available to keep the tank heated. To save the tank water, manually move the tank valve (V6), located under the water tank, to the closed position prior to initiating system purge. Purge the system using the in-air or ground purge method. The system will attempt to purge the tank for 15 minutes. After that time, it will assume that the tank water is being retained and will move on to the remainder of the procedure. The water tank heater blanket can be kept on using ground cart or Auxiliary Power Unit (APU) power during cold weather. With aircraft power on, press the tank heater switch on the tank heater switch panel located in the Baggage Electronic Equipment Rack (BEER).

This process only works if you have power available for the tank heater.


System Start up in Cold Weather Following Purge

Figure: Touch Screen Purge Button, from Gulfstream Video.

[G450 MOL-11-0007] To ensure water doesn't freeze as it enters cold pipes, allow the system to warm up for 20 minutes prior to servicing the water tank. Turn on the water system and press and hold system heat for 3 seconds to activate the system heaters.

After 20 minutes, add water to conformal water tank and open all faucets until water begins to flow. Then you may turn on the “Lav” and “Galley” heaters.


To fill the tank internally:

You can fill the tank externally, but we don't do that. (We don't trust the water the FBO is giving you from the garden hose.)

[Taken from placard behind access door.]

Photo: From Eddie's aircraft.

Turn on ground service bus.

Cycle water system on then off.

Photo: From Eddie's aircraft.

Relieve pressure from water tank by opening the manual relief valve next to the fill cap.

Photo: From Eddie's aircraft.

Remove the fill cap.

Install funnel assembly.

Fill water through the funnel.

Remove funnel assembly.

Photo: From Eddie's aircraft.

Replace the cap. Note: if the cap won't secure, you may have to move the internal spring inside the cap a quarter turn.

Photo: From Eddie's aircraft.

Close manual relief valve.

Turn off ground service bus.


Gulfstream Video:

Water System Purge.


G450 Water System Panel Instructions

There is an eye test on the back of the water system panel that summarizes water system instructions. Because I can't read the panel without a magnifying glass, I've taken a high-resolution photo so I can see it here:


References

Gulfstream GV/G500/G550/G350/G450 Water System Checkout and Troubleshooting Procedure, GV-GER-7690, May 05, 2005

Gulfstream G450 Aircraft Operating Manual, Revision 35, April 30, 2013.

Gulfstream G450 Maintenance Operations Letter 11-0007, Water / Waste (ATA 38) - Cold Weather Water System Procedures, G450-MOL-11-0007, March 4, 2011

Gulfstream Video, "Gulfstream Aircraft Water System Purging," published 5/10/2012, available at www.mygulfstream.com