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Author Topic: Stump the engineer...  (Read 3375 times)
Sean
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« on: May 10, 2010, 03:58:53 PM »

Today we had to remove our Microphor air-operated toilet for the first time in several years, to repair some floor damage.  While it was out I noticed something very strange:



This is a pressure gauge installed on a small brass pressure regulator.  Specifically it is a Watts irrigation regulator, and it is in-line in the water supply to the toilet.  Without this regulator, the toilet tends to use too much water.  The gauge came with the regulator, to facilitate adjusting the pressure.

As you can see, the indicator pointer is bent.  It most assuredly was not when I installed it a couple years ago.

I am mystified.  It looks like the end of the pointer bent on the zero stop.  The only way I can think such a thing could happen is if the water line drew a vacuum, and I would imagine it would have to be a pretty strong one to bend it like that.  I've been ruminating on this all day, and I can't think of a way the fresh water system could do this.

Any thoughts?  Guesses?  Was I parked next to Uri Geller?  Inquiring minds want to know.

-Sean
http://OurOdyssey.BlogSpot.com



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Full-timing in a 1985 Neoplan Spaceliner since 2004.
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cody
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« Reply #1 on: May 10, 2010, 04:00:44 PM »

Burrito's
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Len Silva
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« Reply #2 on: May 10, 2010, 04:05:32 PM »

Got me stumped, but that's a whole lot easier to do these days.  So....

There was air in the system on a hot day and it got quite cold overnight, developing a vacume.

Or,  your water system sucks.
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« Reply #3 on: May 10, 2010, 04:13:45 PM »

  How about High altitude and cold (going over a pass). If your system is sealed this would create a vacuum, would it not? Or like Len said...Your water system sucks...Cable
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Sofar Sogood
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« Reply #4 on: May 10, 2010, 04:35:55 PM »

I would guess when you relieve the pressure before the pump kicks on the needle is slamming to 0 and over time bending each strike of the stop. You might want to go with oil filled gauge. I have looked at and have shown everyone your blog. I don't think your system sucks. lol If I could only have it so good. Grin
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gumpy
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« Reply #5 on: May 10, 2010, 04:45:57 PM »

I'm with Eddie on this. It's slamming against the needle when you flush and the pressure immediately drops to 0 because the line is small, and the valve is big.
Over time, that has caused it to bend slowly.

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Craig Shepard
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Sean
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« Reply #6 on: May 10, 2010, 05:01:27 PM »

OK, that makes some sense.  When I first installed this and tested it, I did see a distinct pressure reading drop every time I operated the flush valve.  However, I never saw it drop all the way to zero.  Perhaps there is some particular set of circumstances (altitude, temperature?) where the drop is taking it to zero consistently.

That said, that's a hell of a deflection for a spring-return needle...

Now that the thing is bent so far that it can drop well below the zero mark, I will keep an eye on it for a while and see what it is doing when the valve is operated.  It's very hard to see, though, when the toilet is back in position.  (It was a bear to install.)

FWIW, if I had it all to do over again, I would have gone with a "normal" RV toilet and a 3" waste angled down to the tank.  It's a run of eight (horizontal) feet or so, which is why we went this way to begin with.  But even if we had to adjust a direct-drop model to use, say, an extra cup or so of water per flush, we'd still be ahead compared to the half-gallon this monster uses.  What it would take to reroute the plumbing now, though, is more of a challenge than I want to tackle.

-Sean
http://OurOdyssey.BlogSpot.com
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desi arnaz
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« Reply #7 on: May 10, 2010, 05:17:14 PM »

i think it went past the 4 not below the zero.......
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« Reply #8 on: May 10, 2010, 05:30:09 PM »

i think it went past the 4 not below the zero.......

The needle is bent the wrong way... Smiley
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« Reply #9 on: May 10, 2010, 06:19:11 PM »

The pointer is plastic.  It got hot and deformed as the spring that returns the pointer to zero applied a slight torque, enough to bend the pointer under the right (read: hot) temperature.  The tip of the point "drooped" over the pointer stop which would not have happened if it was subjected to a force capable of simply just bending it.



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OneLapper
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« Reply #10 on: May 10, 2010, 06:46:25 PM »

Does the gauge measure pressure in the line or directionally as the water flows???

If it measures directionally it would do that with back pressure if your water supply to the toilet was shut off.

Melbo
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Sean
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« Reply #11 on: May 10, 2010, 07:37:07 PM »

Melbo, it is just a plain old pressure gauge.  So flow direction can have nothing to do with it.

OneLapper:  Hard to imagine what could make it hot enough to deform plastic there, but it's possible.  I have no way to know if the needle is plastic or metal.

-Sean
http://OurOdyssey.BlogSpot.com
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« Reply #12 on: May 10, 2010, 08:02:51 PM »

You will have a way to check when you buy your new guage Wink
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Barn Owl
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« Reply #13 on: May 10, 2010, 09:19:31 PM »

An interesting thing I have learned about metal through my job, is that even a small impact force, applied many, many times, can bend and deform a very large and substantial piece of metal. I bet it didn't take a lot of force (relatively speaking) to bend that needle. Just hundreds of slaps on the zero stop.
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« Reply #14 on: May 10, 2010, 10:37:33 PM »

Ever run out of flush water?
Ever freeze that water line? (cold weather)
Ever had a vapor-lock condition in that line? (hot weather)

Any of those would likely cause a good slam on the peg when you flush.
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