How to take the top off this Nautilus pac fab


New member
Jul 3, 2019
Good morning everyone! My house was built back in 1988. I have an Nautilus pac fab filter. Of course you can't read anything on the label. I plan on replacing the filter today. When taking the top off this style where do I release the pressure? I don't see pressure release valve. I'm assuming it will take an wrench to twist to release pressure first. Is that correct?109407109408109409


Mod Squad
TFP Expert
LifeTime Supporter
Jul 10, 2009
Houston, Texas
Hi, welcome to TFP! There should be a knob on the back of the pressure gauge assembly that you can open to release pressure.


TFP Expert
LifeTime Supporter
Jan 6, 2010
San Dimas, CA (LA County)
When the pump is off, there is no pressure. Kill the pump at the circuit breaker, not just at the timer.

If you want to drain it, open the air bleed. It's hard to tell, but it looks like there's a black wing-nut thing like a radiator petcock behind the gauge. That would be it. If it is, be gentle. And it may screw in to open, so try both ways before you start really wrenching on it.

You'll hear air sucking in and the glug-glug glug as it drains down.

If the lid sticks, resist the urge to ram a screwdriver or some other wedge between the shells. You might deform things and then it will never seal properly. Post about it. It may take a while to get a reply, which is why you want the power off, so the timer doesn't come on while you're waiting.


Silver Supporter
Mar 20, 2017
DFW - Plano, TX
I have the NS-48 which is the same, or at least in the same family as yours. Release the pressure, release clamp and give it time. You should then be able to twist the top half off.