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Old 01-07-2019, 08:41 PM   #11
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I can't remember what I did New Years day.
Now I spend every day forgetting things.
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Old 01-07-2019, 10:48 PM   #12
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Larry, Larry, Larry you need a hobby! Water sports maybe?
That explanation was a lot of work on your part (and mine just reading/comprehending).
Thank you.
Now if I go out, remove that back flow device, throw it in the creek behind the RV
my pressure relief valve will stop dripping.
Yes!!!
Oh, BTW, if one of these Florida alligators in the creek swallows that back flow preventer will he/she “pressure up” and start to drip?
Travel safe
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Old 01-07-2019, 11:10 PM   #13
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Somehow I would be interested WHY all those fittings including the HOT WATER heater popoff valve were leaking.

Was every one of these leaks due to an ill fitting threaded fitting?
Was there some PEX fittings that leaked?
Why would the heater valve also leak?

Could the water inlet pressure be too high? Seems that some connections would have been water tight, unless a 12 year old worked on doing the water connections in your trailer...
Every single threaded connection was either cross-threaded or the sealing surface damaged. All but the shower/tub connections were repaired by disconnecting, inspecting the threads, cleaning them up if needed, then screwing them back together. Shower/tub connectors were replaced as they'd been too damaged to repair.

The leaks have happened over the course of 14 months. Water pressure is from a well pump that feeds 3 separate residences - house, mobile home, travel trailer. TT is about 300+ feet from well, line is 1-1/2 inch, and there is about a 6-8 foot height drop. Pressure at TT varies due to the vagaries of who is using water when, but pressure switch is set at about 45-50 psig. Pressure drop caused by distance & line is pretty much made up by the extra head from the elevation difference.

Pretty much all the many problems we've had with this TT are QC related, as in there was no QC! Aside from the no-QC issue, there are so many design/engineering flaws that make it difficult to perform maintenance/repairs. But I've only worked at one place where the engineers/design pukes bothered to listen to the assemblers/techs who had to work on things. It's all made to slap together as quickly as possible, and damn the techs who know what a wrench is and where it will fit, LOL!
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Old 01-07-2019, 11:33 PM   #14
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No check valves, except the foot valve down the well, that I know of, and this was the first time we've seen the relief leak. No water was being used, nor had been used for about 1/2 hour. The heater had kicked on while THE MAMA was outside walking the muttslies.

The house on the well has no expansion tank, and while we go through water heaters regularly due to the low pH, we've never seen a relief valve leak. Reckon we'll be keeping a close eye on it.

Enjoyed your explanation! I am, er, was an Instrumentation/Electronics tech in a power plant. I knew little about piping systems, except some bits remembered from mu nuc power days. That changed some when a boss told me to install a pump and line to route regeneration water from a demineralizer regen tank to an "ecology pit." Learned all about the pressure drops associated with different sized piping and the number of what kind of fittings, distance involved, and the change in elevation. It was a nice little program - plug the numbers in, and it chugged away, giving the specs and the whys, too. It told me I could run a slightly smaller line from the well because of the drop in elevation from the well to the site. Considerably less expensive!
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Old 01-08-2019, 10:08 AM   #15
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Static pressure

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Originally Posted by Pococj View Post
Pressure at TT varies due to the vagaries of who is using water when, but pressure switch is set at about 45-50 psig. Pressure drop caused by distance & line is pretty much made up by the extra head from the elevation difference.
If you don't believe in science, stop reading now.

Many people fail to consider something called "static pressure." This is the pressure in a fluid line when no fluid is flowing. It is constant everywhere inside the line. Everybody seems to intuitively understand Bernoulli's Principle where pressure is reduced after a necked-off point, even if they don't know the names or equations behind it.

What they don't get is that part of the equation is the flow rate. If the flow rate goes to zero, there is no flow and there is no reduction in pressure. Those people who think they can reduce the water pressure in an RV by turning the pedestal valve nearly closed are deluding themselves. As soon as water taps in the RV are shut off, the pressure will rise to the same pressure as behind the pedestal tap, even it if's only open a pinhole. Even my son, who has a bachelor's and master's in engineering, got trapped by this one. To his credit, as soon as I asked "What about the static pressure?" he immediately got it.

In the sentence quoted above, head (water pressure difference due to height difference) will make a difference but the line length and diameter will not, whenever there's no flow.

Larry
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Old 01-08-2019, 10:22 AM   #16
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Larry, Larry, Larry you need a hobby! Water sports maybe?
Going snorkelling in the Caribbean at the end of the month! That should do it.
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Originally Posted by FordHaul View Post
That explanation was a lot of work on your part (and mine just reading/comprehending).
Thank you.
It was harder than I thought it would be. I hadn't remembered that the thermal expansion coefficient of water varies with temperature. Then I wasted a few minutes looking for a reasonable online calculator where I could simply enter starting and ending temperatures and get the volume change. To my surprise, I did find one or two but they didn't exactly meet my need. I wound up creating a spreadsheet (available on request), where I calculated the increased volume for a 10-degree span, then calculated the increase of the new volume for the next 10-degree span with a different coefficient, etc. Yes, that's an approximation, but good enough to make the point.
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Now if I go out, remove that back flow device, throw it in the creek behind the RV my pressure relief valve will stop dripping.
Yes!!!
As long as the water pressure is lower than the value set for the T&P valve, the drip should stop. There can't be other check valves/backflow preventers hidden someplace.

There was a period of time when the city had put a backflow preventer at the water meter but I had not yet installed an expansion tank. The travel trailer was in the driveway connected to the house's water. There was no backflow preventer on the hose tap. The trailer's valve was dripping--and so was the water heater within the house! That's what finally led me to install the expansion tank. You can't fight city hall.

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Old 01-08-2019, 10:40 AM   #17
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Wife and I sat on the couch...or laid....due to the flu. NO ! don't want do that all year.

Larry needs a hobby.
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Old 01-08-2019, 10:44 AM   #18
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Quote:
Originally Posted by Larry-NC View Post
If you don't believe in science, stop reading now.

Many people fail to consider something called "static pressure." This is the pressure in a fluid line when no fluid is flowing. It is constant everywhere inside the line.

...head (water pressure difference due to height difference) will make a difference but the line length and diameter will not, whenever there's no flow.

Larry
Understand what you're saying. I failed explaining - I was originally worried about the pressure drop because of the distance from the well. THE MAMA would not have been happy if her shower was a dribbling experience.

One of the problems I used to run into at work was having a calibration gas regulator fail, causing the outlet side pressure to start slowly climbing to the bottle pressure, which could be as high as 2200 psig. If my guys missed noticing the regulator outlet gauge climbing, they'd get a surprise when one of the teflon lines inside the shelter blew up.

Again, thanks for the explanations.
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Old 01-08-2019, 10:46 AM   #19
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On the bright side, I haven't worked on a leak for 3 days.

(Smartly raps head with a closed fist, simulating 'knocking on wood.')
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