Confused about new liquid-filled pressure gauge

[Rocket J Squirrel]

The pressure gauge on my Pentair cartridge filter is starting to stick. So I bought a fancy new liquid-filled gauge from TFTestkits.

There are 2 conflicting instructions about venting the gauge. One says pull the plug and push it back in. The other says pull the plug halfway and leave it there. The URL on the paper insert does not exist.

Which is better? I should add the pin is really small, pops right out, and will be extremely easy to lose if it drops to the ground. So I'd prefer not touching it too often, but I'd worry having it halfway in would tempt it to pop out and disappear.

 

[JoyfulNoise]

Honestly, opened or closed never made a difference for my readings. My gauge prematurely died by getting crud plugged up inside it. You can test it open or closed to see what happens. If it’s going to see a lot of rain, then best to leave it closed and only open it when you want to make sure your reading is accurate.

 

[Rocket J Squirrel]

OK, now my problem is removing the old gauge from the pressure relief valve. They seem permanently mated. I'm afraid brute force will crack the plastic before the gauge unscrews. I put some 3-in-1 oil on it & will let sit overnight.

I thought perhaps I could just buy a new relief valve for the new gauge, but they seem to be only available as a package. I can't seem to buy part # 98209800 without also getting part # 190058 if you're into Pentair part numbers.

 

[Rocket J Squirrel]

The overnight oil soak worked. New gauge installed.

Ran the pump, pulled the little gauge pin and put it back. All fine. Then I increased the pump to high speed. looked at the gauge. No pin. It had popped out under pressure and vanished. After 5 minutes on hands & knees, I found it. Happy ending but not as trivial as I'd imagined.

 

[Brett S]

I’m getting in on this thread a little late, but I’ve been leaving my gauge closed. However, I have noticed that temperature definitely makes a big difference. Say I vent the gauge in the morning when the temp is cool and the gauge isn’t in the sun, then close it. Then I come back in the afternoon when the it’s hot out and the gauge is in direct sun and vent it again. The reading will drop by a good 2-3 PSI. So what I’ve been doing is trying to read the gauge at about the same time each day, and/or vent it before I read it.

I don’t recall seeing that little sheet that suggested leaving it open, but I had considered leaving it open. My concern with that would be that water might get into the gauge when it rains and damage it.

 

[Rocket J Squirrel]

The reading will drop by a good 2-3 PSI.

That's not good. I thought the point of the fancy liquid-filled gauge was to be more accurate than the standard Pentair gauge. If I find I have to play with it to get accurate readings, I'll replace it with the OEM gauge.

 

[Brett S]

That's not good. I thought the point of the fancy liquid-filled gauge was to be more accurate than the standard Pentair gauge. If I find I have to play with it to get accurate readings, I'll replace it with the OEM gauge.

I believe that the standard gauges are affected by temperature changes just as much, if not more, but they have no way to equalize the pressure, so it might not be as noticeable. But the error will still be there if you read when the gauge is cool and compare it to a reading when the gauge is hot.

 

[goody222]

I ran into this same situation also. I keep the pin on my gage pulled halfway out. Then, whenever I go to read the pressure, I put my finger lightly on top of the pin and wiggle it gently. Then the arrow will drop to the correct pressure. Only takes 1 second of effort. The build quality of this gage is SO much better than the cheap plastic one that came with my filter. housing.

 

[revitup]

The original gauge on our Hayward sand filter never varies with temperature.

 

[Brett S]

The original gauge on our Hayward sand filter never varies with temperature.

In my (admittedly very limited) understanding of how these gauges work, I don’t think that’s actually possible. I’d love to see you test it by reading the gauge first thing in the morning when the ambient temperature is low, and then again that same day in the afternoon when it’s hot out and the gauge is in the sun. Preferably with the pump at a high speed, if you have a variable speed pump, since the difference should be more noticeable at higher pressures.

Not a big deal if you don’t want to bother testing, it’s more just for my own education because, like I said, I only have a very limited knowledge about this.

 

[Rocket J Squirrel]

In 8 years of running Pentair cartridge filters with their OEM gauges, I have never once seen my pressure change at normal pump speed. It only changes when pump speed changes. My filter sits out in the blazing sun and temperature has never affected the OEM gauges. I will have to observe the new liquid-filled gauge.

 

[Brett S]

So I got curious about this and I did a little more reading. And apparently the difference is that the dry pressure gauges are all vented to the atmosphere, so it’s not possible for pressure to build up inside them with temperature changes. However, this also has the downside that during humid conditions or even during rain it’s possible for small amounts of water to get into the gauge and this is what can cause the gauge to fog up or even cause corrosion on the internal parts and cause the gauge to fail.

The oil filled gauges are typically sealed from the atmosphere (unless you open the vent) and as such they are affected by ambient temperature changes. However, they have the advantage of being more accurate and lasting longer.

 

[Rocket J Squirrel]

I think I'm start to hate this gauge. Yesterday it was reading low, so I pulled the pin. Pressure reading went to normal, but I got oil on the gauge and on my fingers. A small amount just gooshed out. This doesn't seem sustainable. How much fluid can I lose before the gauge is a dead soldier?

 

[markayash]

I lost my pin months ago and it still works perfect. I can see 1/2 differences with no issues. Maybe you got a damaged gauge?

 

[Dave_NJ]

My gauge spit out a bit of oil when I pulled the pin the first time. With the pin out I squeezed the gauge just enough to get a bit more oil out then I put the plug back in.

It's common for liquid gauges to have a small air bubble at the top to allow the fluid to expand without coming out of the pressure port.

 

[CRAD_oz]

The Glycerine inside the Pressure gauges main purpose is for dampening of the needle in a fluctuating pressure procces. As Brett s also noted it's to prevent moisture corrosion on the internal gears and bourbon tube. The gauge internals should be vented when in service and closed for transport.
You probably won't notice much difference in pressure readings with the gauge internals closed off in the cooler months of the year.
Non Glycerine filled gauges are open to atmospheric pressures.

 

[Rocket J Squirrel]

I really just glance at the gauge as I pass by my equipment. When I saw it was reading lower than usual, I knew something had to be wrong, since pressure can only go up over time as my cartridge filter accumulates crud. Pulling and replacing the pin restored accuracy, but it leaked fluid. If I have to fiddle with it to get an accurate reading, and wipe oily fluid off my fingers each time, meh. More trouble than it's worth, especially since my pressure really never changes. I'll try leaving the pin halfway out.