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Old 03-29-2020, 06:00 AM   #1
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Plumbing and/or Physics Question...

OK the basic question: keeping in mind that the mass of air and water are greatly different...,

...is 200 psi of air pressure the same as 200 psi of water pressure?

Background:

My friend was having plumbing issues with his rig a few weeks back. Low flow from the majority of his faucets, shower, and even toilet. Heíd already removed the shower & sink faucet heads, and soaked them in CLR... plus drained & flushed the hot water tank, but he still low flow even though there was good pressure at the campground water taps (verified by gauge).

Had a mobile tech come out... and after he did his initial checks, he proposed to put 200 pounds of pressure in the lines to really blow them out. My friend, of course, was hesitant because heíd always read that anything over 60 psi was asking for trouble. The tech said... ďthis ainít water, this is air.Ē

After some discussion, and the tech agreeing to repair any burst lines as a result for parts cost only... my friend agreed. The tech attached the air hose, pressurized the lines, and then my friend went inside and opened the faucets one at a time. He said all kinds of crud flew out of each one... and at the end, no leaks & no burst pipes.

The end result is that he has better flow in his shower now than at home. Told me everything is working great... good flow everywhere... and no complaints now, which is 10 weeks later.

So now Iím thinking of doing similar with my air compressor... only at 150 psi, which is its max. But Iím scared as hell to do it.

Iíve been right on the Colorado River all winter, and the water here is notoriously hard. Iíve been soaking my own shower & sink faucet heads in CLR about every 6 weeks, and just did another hot water tank flush earlier today (my 2nd since I got here in October). As expected, lots of white calcium deposits came flowing out.

Well, even with that, my flow rates are drastically lower than I remember them last summer. Theyíre not God-awful, mind you... but not great at all. And yet the gauge on my water regulator from the campground water tap shows a good 65 psi... right where I have it set.

So Iím thinking of doing the same high-pressure air routine like my friend did... but not being real comfortable doing plumbing work, Iím hesitant to go thru with it.

Curious to read any thought you guys might have about it. Itís that statement the tech made... ďthis ainít water, this is airĒ... that gets me, as on the surface I donít see a difference. 150 psi is 150 psi, regardless of the component causing it. But just figure that maybe with the mass of air being far less dense than water... maybe it isnít.
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Old 03-29-2020, 12:05 PM   #2
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Hi guys, I bought one of these and it's GREAT!

https://www.rvwaterfilterstore.com/W...waAo8pEALw_wcB
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Old 03-29-2020, 01:31 PM   #3
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I agree with you that 150 psi is 150 psi.

Since your buddy was kind enough to be the ginny pig and suffered no ill effects, I think if it was me, I would wait until I got back near civilization just incase something did go wrong. Knowing the quality of supplies that Dutchmen uses, I sure would hate to have a ruptured water line out in the boondocks.



Disclaimer: I failed high school physics, so one person's 150 psi could really be another person's 250 psi. 🤔
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Old 03-29-2020, 01:54 PM   #4
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I had to replace almost all my water lines in my voltage I found that some of my water lines were not even on all the way from factory from what Iíve seen in our rv if you happen to blow some lines off you would also strip threads off. just sayin all our best FLA
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Old 03-29-2020, 02:11 PM   #5
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An interesting take on pneumatics v hydraulics.
https://medium.com/@Lifting_Equip/hy...n-ab593b1d4345
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Old 03-29-2020, 02:37 PM   #6
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I boil oil for a living, 200 psi is 200 psi whether it is a liquid or a gas. A gas is much more compressible than a liquid (volume it occupies gets smaller). A compressed gas has more stored energy than a compressed liquid when released. Things have a max design operating pressure and a mechanical test pressure (structural). The mechanical test pressure is typically 1.5 times design. If the max water pressure is 60 psi, the maximum pressure you should put in the system is 90 psi. At 90 psi you risk a failure at a an existing weak point. Going over this test pressure greatly increases the risk of creating a failure at the weakest point or a new weak point from the added stress that will become a future failure point. Things can fail the 1.5 typical test pressure, but is very rare.
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Old 03-29-2020, 08:09 PM   #7
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I appreciate all of the feedback... though I'm still undecided about blowing the lines with that much pressure. I may just try it at a lower pressure (80-100 psi) at first to see how it goes.

I'm in Bullhead City, AZ... so not completely away from civilization... and I do have a mobile tech here that I trust should any serious plumbing issues arise. I just don't wanna be the cause of any major issues, especially since the system has worked damn-near flawlessly since I bought her new back in 2013. Only problem I've ever had was a leak from one small check-valve, and that was within the first year. So I'm not sure tempting fate at this point is wise.
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Old 03-29-2020, 10:49 PM   #8
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From a technical spec page on PEX.

Since all PEX tubing used in the US is manufactured to the same ASTM and dimensional (SDR) standards, these specifications are universal.
74įF at 160 psi is the maximum test pressure.
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Old 03-30-2020, 12:54 AM   #9
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Quote:
Originally Posted by ATCguy View Post
I appreciate all of the feedback... though I'm still undecided about blowing the lines with that much pressure. I may just try it at a lower pressure (80-100 psi) at first to see how it goes.

I'm in Bullhead City, AZ... so not completely away from civilization... and I do have a mobile tech here that I trust should any serious plumbing issues arise. I just don't wanna be the cause of any major issues, especially since the system has worked damn-near flawlessly since I bought her new back in 2013. Only problem I've ever had was a leak from one small check-valve, and that was within the first year. So I'm not sure tempting fate at this point is wise.
My take on all of this is that you have to have a faucet open at all times.. Always open the next one before closing the previous one. You may start with a 200 psi pressure in the compressor, but you are blowing air thru an open line at a high velocity. The line never gets to 200 psi and might not even get to 90 psi, because one end is open.

A low tech way to do it would be that you could put white vinegar in the water lines to dissolve the scale. Its even compatible with aluminum tank water heaters.. Its anti-bacterial.. rinses out without leaving a residue and its cheap.. The only drawback would be that you would have to leave the vinegar in the lines at least overnight.

Oh well that's just my 2 cents..
Lots of ways to "skin a cat"
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Old 03-30-2020, 01:16 PM   #10
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Quote:
Originally Posted by Firstime RVer View Post
My take on all of this is that you have to have a faucet open at all times.. Always open the next one before closing the previous one. You may start with a 200 psi pressure in the compressor, but you are blowing air thru an open line at a high velocity. The line never gets to 200 psi and might not even get to 90 psi, because one end is open.

A low tech way to do it would be that you could put white vinegar in the water lines to dissolve the scale. Its even compatible with aluminum tank water heaters.. Its anti-bacterial.. rinses out without leaving a residue and its cheap.. The only drawback would be that you would have to leave the vinegar in the lines at least overnight.

Oh well that's just my 2 cents..
Lots of ways to "skin a cat"
EXACTLY!
The 200 pounds of air pressure is what "he is pressurized to" and pushing out into your plumbing. You will "always" have a faucet open so that "amount of force" is pushing only against obstructions. 100 - 150 PSI may also be adequate, the key is to ALWAYS have a faucet open.
The only way your plumbing is going to feel any pressure whatsoever is if you closed ALL faucets and/or someone pushed a rag or some tight-fitting object into your plumbing lines somehow...
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Old 03-30-2020, 02:48 PM   #11
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He probably expanded the lines like a balloon, breaking the “crud” loose So it could be blown out. I’m not sure how much pex lines can expand but I know they freeze well and expand some. It’s the connectors (plastic) that’s the weak point. Not sure about brass but I am really sure that our fantastic RV manufactures would not be using things that are that expensive.

In my humble opinion, 200 psi is 200 psi
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Old 03-30-2020, 02:57 PM   #12
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PSI is PSI

Quote:
Originally Posted by franktafl View Post
He probably expanded the lines like a balloon, breaking the ďcrudĒ loose So it could be blown out. Iím not sure how much pex lines can expand but I know they freeze well and expand some. Itís the connectors (plastic) thatís the weak point. Not sure about brass but I am really sure that our fantastic RV manufactures would not be using things that are that expensive.

In my humble opinion, 200 psi is 200 psi
Yes, the "Crud" will be picked up by the tremendous air mass as it tries to pass. It will push any structure blocking the pipe out the faucet. (You may want to remove any faucet screens if you have really low water pressure!)
LOTS of air pressure will move into your plumbing and try to "normalize" (Equalize) the pressure between the air pump and your pipes until or if equal pressure is obtained. You do not want this!!!!! That is why one faucet is always open. You will just have a lot of moving air out of your open faucet, do this until each faucet has been cleared. Always open the next faucet before closing the current one.

...and yes 200 PSI is 200 PSI
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Old 03-31-2020, 02:44 PM   #13
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I like Firstime RVer suggestion about using white vinegar. Bypass the water heater and fill the water lines using the winterization connection at the pump suction. Let sit overnight and then flush out the lines with fresh water after removing all faucet screens.
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Old 03-31-2020, 03:47 PM   #14
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I like Firstime RVer suggestion about using white vinegar. Bypass the water heater and fill the water lines using the winterization connection at the pump suction. Let sit overnight and then flush out the lines with fresh water after removing all faucet screens.
But be sure you have a water heater bypass before you add the vinegar.... My unit does not have a bypass that I can locate on the unit or using the model number for the online manual.

However, I have not been able to give it a serious look since my unit is at the Dealer.

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Old 03-31-2020, 10:58 PM   #15
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But be sure you have a water heater bypass before you add the vinegar.... My unit does not have a bypass that I can locate on the unit or using the model number for the online manual.
When you get your trailer back look inside where the water heater is located on your trailer. I have a panel I can remove in my lower cabinets in the kitchen to access the back of the water heater and breaker panel. This is where my water heater bypass valve is located. My water pump/winterization valves are located behind a panel under my bathroom sink.
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Old 03-31-2020, 11:25 PM   #16
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When you get your trailer back look inside where the water heater is located on your trailer. I have a panel I can remove in my lower cabinets in the kitchen to access the back of the water heater and breaker panel. This is where my water heater bypass valve is located. My water pump/winterization valves are located behind a panel under my bathroom sink.
Thank you, I will look whenever that date occurs! LOL! Hey, you have to laugh!
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Old 04-01-2020, 12:37 AM   #17
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Use a water softener!
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Old 04-03-2020, 03:32 PM   #18
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But be sure you have a water heater bypass before you add the vinegar.... My unit does not have a bypass that I can locate on the unit or using the model number for the online manual.

However, I have not been able to give it a serious look since my unit is at the Dealer.

MY RV
Days at my home or in my possession since purchase: 7
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If your water heater has an aluminum tank there is no problem running vinegar thru it.. Aluminum handles acid very well, but whatever you do never let it come in contact with any basic or caustic solution..
If you want proof, take a couple of aluminum pans or cupcake tins.. fill one with vinegar overnight, take the other one and put in some warm water and crushed limestone.
See which one has a hole in the bottom the next day!!
You could use lye but that would eat out the bottom in just an hour or two..

If your water heater is galvanized.. Be sure to bypass it or Don't use vinegar!!!
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Old 04-04-2020, 01:03 PM   #19
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Originally Posted by Firstime RVer View Post
If your water heater has an aluminum tank there is no problem running vinegar thru it.. Aluminum handles acid very well, but whatever you do never let it come in contact with any basic or caustic solution..
If you want proof, take a couple of aluminum pans or cupcake tins.. fill one with vinegar overnight, take the other one and put in some warm water and crushed limestone.
See which one has a hole in the bottom the next day!!
You could use lye but that would eat out the bottom in just an hour or two..

If your water heater is galvanized.. Be sure to bypass it or Don't use vinegar!!!
Thank you, YES! I comprehend, I am an old (Mad) Scientist) so that was an old H.S. Chemistry FUN TIME experiment.

On a more somber note, I was just advised Thursday that I would not see my new RV until "sometime after this Pandemic was over" per my Dealer. I picked the wrong time to buy a piece of %^&! Thank you Dutchman, Thank you Gander RV of Atlanta! They should BOTH thank their absolute lucky stars I do not have a fatal condition...
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Old 04-04-2020, 02:40 PM   #20
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Maybe you can try to get them to extend your warranty by six months or so. I doubt it but try it. I would go with the pleasant approach first and then if it doesnít work try another.

Regardless, you should immediately take a few trips and get it back in to fix the new stuff you notice then bring it back in a final time right before the warranty end date to fix the rest of the stuff. However, if the new stuff is minor or tolerable donít take it in until the very end of the warranty period because you will lose opportunities to identify issues.

Sorry for your BS. I had issue with mineólots of issues some they fixed under warranty and others like the crap suspension I had to replace on my own nickel but it is pretty dialed in now and we really enjoy it.

Keep in mind they start with a cheap frame by some other manufacturer and then they bolt on a bunch of cheap components and this is what you get. The good news is there are forums like this to help us all get them working again and the sad reality is they are expensive purchases and expensive and time consuming to maintain, but still can provide a great deal of enjoyment.
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