# Geolocation has wrong elevation

#21

do you really have 104’ of head?

#22

There is over 875’ horizontally between the upper tank and the hose bib where I attached the gauge (it is at a lower tank which is shown on the attached SketchUp drawing) so I can’t easily determine the elevation with a survey and I don’t have sophisticated survey equipment. The most accurate measure I have of the elevation difference is the measured pressure which has been measured at various times in the past. The consistently measured pressure is about 46 PSI. It will vary a bit depending on the level of water in the upper tank. The elevation difference measured on Google Earth is 95’. Google Earth is not very accurate. 95’ corresponds to a pressure of 41 PSI which is reasonably close considering the uncertainties of Google Earth.

The big question is: What mechanism could account for measuring 15 PSI, and for that measurement being different at different times (sometimes 46 PSI) when nothing is physically different in the pipes and tanks? And for it changing from 15 to 46, again with nothing physically different in the pipes?

#23

Forgot to attach the file. Here it is.

#24

(Forgot to attach the file, so here it is)

There is over 875’ horizontally between the upper tank and the hose bib where I attached the gauge (it is at a lower tank which is shown on the attached SketchUp drawing) so I can’t easily determine the elevation with a survey and I don’t have sophisticated survey equipment. The most accurate measure I have of the elevation difference is the measured pressure which has been measured at various times in the past. The consistently measured pressure is about 46 PSI. It will vary a bit depending on the level of water in the upper tank. The elevation difference measured on Google Earth is 95’. Google Earth is not very accurate. 95’ corresponds to a pressure of 41 PSI which is reasonably close considering the uncertainties of Google Earth.

The big question is: What mechanism could account for measuring 15 PSI, and for that measurement being different at different times (sometimes 46 PSI) when nothing is physically different in the pipes and tanks? And for it changing from 15 to 46, again with nothing physically different in the pipes?

#25

an airlock somewhere in your pipe run is the only thing I think can cause the variance…
without the skp [still unattached] it’s difficult to know if the pipe is undulating over it’s 875’ traverse…
any slight down slope could provide an air lock…
john

#26

Here is link to explain in more detail, looks like john hit target. You may be able to install some bleeds at high points in your system to prevent. https://en.wikipedia.org/wiki/Air_lock

#27

look for an air lock 37.1 feet ‘above’ your gauge if it’s reading 15psi…
john

#28

The skp file is 20 MB. Is that why it didn’t come through? If so, how can I post it? (Large size is because of the Google Earth topography).
Is an airlock a place where the pipe goes up and down in a U?

#29

I think that is called a “trap”. An airlock might be trapped on the lower side of a low spot.
(That is the purpose, to trap gasses from advancing up the high side of the line.)
https://en.wikipedia.org/wiki/Trap_(plumbing)

#30

going up in relation to the fall is the issue that can create an airlock…
so, more like an upside down , if filled slowly water can become locked by the air caught in the top…
a vent at that position would allow the air out and it will be replaced by water…

john