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Old 05-07-2021, 07:39 PM   #1
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45 PSI AND NOT MUCH WATER PRESSURE - Is this really possible?

I'm in an RV park wit 45PSI, but I can't seem to get normal water flow out of my kitchen faucet, shower head or sink.

I have a 2004 Itasca "Horizon" 40AD and I just installed a residential 3/4" inlet water filter from Lowe's, because my old filter blew-up in the Texas freeze last winter.

So let this be a lesson to us all: When you winterize don't forget to empty your water filter and drain your washer dryer too!

Anyway, it's not City Water Fill Diverter Valve; and I don't know where the check valve is to the water pump, maybe someone can send me a picture, but as I have read in other threads, if your fresh water tank is not filling up them the pump check valve is not the problem either.

So can all of this be reduced flow through my new water filter? ...Even when I'm using the same filter media, which is a large particulate mater type, and which in the past was okay with my older style Home Depot brand water filter. (HDX it think it was called.)

OR... Is it the RV park pump is able to produce 45psi but it has very poor flow rate?

Oh yes... One more clue. When I turn on my 12V water pump I have normal flow to my kitchen, shower and faucet so I know I'm not dealing with a blockage issue.
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Old 05-07-2021, 07:54 PM   #2
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I would suspect the new filter cartridge but would it be easy to take the cartridge out and see how the flow is then?

But there is also something to question on the pressure as we have used a brass pressure reg that does give really bad flow when we have it in the line. Apparently is works by restricting flow more than pressure.

I might suggest trying with/without either of these to see what result you get.
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Old 05-07-2021, 09:15 PM   #3
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Yes. I realized after I posted this thread I would have to bypass the filter to rule it out.

It was my last option as I have to disassemble the hose fittings to the filter, and because of the way the hoses attached it's kind of a PITA, but that's what I need to do next.

Mind you, I'm still using the same filter media a I have always used without a problem, but the filter brand and housing is different. It's supposed to be for houses, and it has a 3/4" thread in and out, but maybe this cheaper version is more for drinking water. If it is a low flow filter then bypassing it is the only way to find out.

Another symptom is that I have acceptable flow for about 1 minute and then it is reduced to a much lower, unacceptable flow rate.

I think I have to mess with it tomorrow. In the meantime, thanks for help.


* Is there a check valve inside my pump, and to get to it do I have to dissemble the lower portion of the water pump?

* When people talk about an RV regulator, can I assume we are talking about that 4" brass regulator I screw on at the hose bib or is there another regulator inside the water pump?

* My pump is working fine and when I turn it on I have normal water pressure. However, I can't tell if it is drawing water from my fresh water holding tank or from the water hose?

==> Clearly the pump is drawing water from the tank, when I am boondocking, but when you are connected to city water... is the water pump still drawing water from the fresh water holding tank?
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Old 05-08-2021, 08:34 AM   #4
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Did some looking and study but you have two problems that leave me guessing some. One is your RV has very complex plumbing with lots of options but hurting even more is the older , before 2010, are not well supported with the super nice interactive drawings so we can't turn things around to get a better view!!!
So the questions for you as you look at it?

This drawing of the filter looks like a pretty standard cartridge filter and I had assumed one could unscrew the housing, take the cartridge out and put the empty cartridge holder back in place. Is that possible or just my imagination?
I was thinking that might make it simple to test with/without the new cartridge for effect. But may be totally bogus!!!

Then some questions on what I see from the backside of the wet bay leads to more questions. Can you turn this drawing around in your mind as if looking from the other side and tell me what valves are where and also verify it is correct for your RV?

What are the three pipes that appear to go out labeled A-11? Not familiar with those.

Click these snips to get better view!
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2015 Winnebago Vista 31KE on 2014 chassis
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Old 05-08-2021, 09:16 PM   #5
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Morich: Thank you for doing some leg work for me. Your efforts motivated me to do some troubleshooting to solve this problem, and this is what I found:

A) The screen and rubber washer in the hose after the filter was full of sediment. I thought this might be the source of the problem, but it wasn't.

B) I then found that rubber valve that allows you to choose between City Water Fill" and "Water Tank Fill" was all busted up inside; and I thought some part of it may be clogging my line, but that was't the problem with low pressure either.

C) So, then I bypassed the water filter and reconnect the hole and I measured 40PSI, but I still had low water pressure out of my shower after 30 seconds, and after 1 minute the pressure was unacceptable.

==> Then I turn on my water pump and all was normal, suggesting I don't have a clog somewhere else in the water lines.... except maybe between the filter inlet and the Diverter Valve valve.

==> But that could be the problem, I thought, because that screen I told you about most certainly would not let any filter media or debris pass any crud through the water inlet hose; so I really have no reason to believe I have a blockage problem.

* This has to be a classic case where PSI does not mean you can count on goo water flow measured in gal/min.

D) So, then I decided to steal the Diverter Valve valve parts out of a new Diverter Valve I keep as a spare, and I replace the guts inside the old Diverter Valve.

...And now my pressure climbed up to 45 PSI, and now my water flow out of the shower is better, but still not acceptable; and I'm back to using the water pump to get good water pressure in my shower head, sink and toilet.

I'm really surprised I can get 40-45PSI... and wash my car with a cleaning wand, which has no real back pressure to speak of, but I can't get enough volume of water out of my faucets or shower head.

So I really can't do more until I move on to another RV park that has better flow rates in there water service.


1) Don't try to replace the valve.

2) Just replace the juts of the old valve using new parts you take out of any Flare-it Fitting that has a turn-valve.

3) Be sure to align the valve with thickest part of the rubber insert FACING UPWARD.

4) Cover the thick part of the rubber insert with the valve plastic fingers. ...It only fits one way.

5) Push the valve body into the old Diverter Valve valve; and align the rubber tabs on the bottom right.... so you can push the rubber insert all the way in. (Do not force it too much. Those plastic fingers are fragile.

6) Reach up from behind your panel and lift the PEX hose so you can screw the face of the valve down. Then just add the turn-arm and you are done!

The attached pictures will help to reinforce what I have described above.

When you open up the system, your 12V water pump may get an "air lock" that needs "burping." To do this, just open up the water outlet valve after the pump and purge the air gap/bubble that is interfering with the water flow.

Then go to your hot water tank (with no water pressure in the hose and your water pump off) and open the "over flow valve" to let water out of the hot water tank. This will lower the water level in the hot water tank, which will help your hot water flow better to your shower head.
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Old 05-09-2021, 09:02 AM   #6
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I see now that my theory of the valves and location was way off, confusing norm/fill valve and antifreeze suction valve.
So with a different view and your info on the diverter valve plastic degraded, I would have a different idea of chasing this problem.
It is often true that we can confuse pressure with the very closely related volume of water.
It is often a hot subject when we speak of having the same pressure on a 1 inch city water line as we have if we use a three inch water line. Folks do often confuse the volume you can get out of a three inch main with the pressure we get on either a one or three inch! You do get a lot more water volume from the larger pipe but the pressure is the same!

But that is where I think your problem may be. You can get water but the volume is different at different points, so I would look at it as problem of something restricting the flow (volume) which does not restrict the pressure.

We can get this if a piece of the plastic from the diverter valve goes downstream a bit and then stick in some place like a tee or el. Water pressure remains the same but water volume can be restricted and we think of it as less pressure if we don't actually put a gauge on to check. Example is if we fill a jar at one point in X amount of time and it takes twice that amount of time at another point, we often say we have different pressure when it is actually volume we are judging!

I would propose looking for that restriction by trying to start at the city water input and move along the line, checking volume/flow at each point along the line until we found where it suddenly drops.

I drawn this snip to try to show what I think might be needed.
Starting at the input for city water, it goes almost directly to the stool and we would think good flow at point 1, onto point two where it goes back out to the outside shower and also tees to point three which goes somewhere I did not ID before going down to a valve which looks like it might be next to the pump(???).

So a big question on that valve? Does it go past the pump or does it have a tee that gives the pump water? I might want to assure this valve is totally open and not cocked partly closed to restrict the city water flow at that point.

Then a weird theory to explain why turning on the pump might make the water flow seem better for a minute but then drop again? If the pump has full water lines but can't get full water flow on the intake side, would it then pump what water it had but then reduce to the amount it can get into the restricted intake?

Or am I just building fairy tales in the sky!!!
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Old 05-09-2021, 04:54 PM   #7
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Again, it is so nice to have someone (like Morich) to help motivate us all to keep going.

Today I was about to open an inspect the "Winterization Valve" to see if anything got stuck, which might be obstructing the flow. ...And on my way back to the water bay I passed by the hose bib and saw that I still had the Camco 4" water pressure regulator connected.

Ug. I thought I removed that thing with all the other combinations and tests I did, but apparently not.

So I removed it and connected the hose direct to the hose bib, and my water pressure measured after the new water filter was 50PSI. And the water flow inside my RV was real strong, maybe too strong.

So now I have determined that Camco Pressure Regulator was cycling good-to-bad, but mostly stayed in the bad position.

This allowed the PSI to build and hold steady, but it interfered with the water flow to my sink, faucets, and shower head.


I think I will look into a Watts adjustable pressure regulator or some other type. I have had these Camco type regulator go screwy before.

TIP: Definitely use a rubber washer with a metal screen. This will keep debris and sediment (rocks) out of your water system; and give you peace of mind should you ever get befuddled like I was this time around!
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Old 05-09-2021, 05:16 PM   #8
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Good thinking with swapping out the reg, we find it cuts our shower too far too be happy, so only use the reg when we are in areas where we might expect high pressure.
In our case we only sense the lack of flow in the shower.
Thinking of how the water sytems generate pressure, by elevating the storage on towers or setting the tank on high ground, we feel safe using the lines without a reg in places where there are no tall mountains tall enough to generate more than 50 PSI as we are not expecting the water folks to build towers taller than necessary!
But if we go toward either mountain range where they are prone to setting thigs up too high for safe use, we do try to add the reg.

Cut and copy info:
Each foot of elevation change is equal to 0.433 PSI of water pressure. Think of a vertical column of water. At the bottom of the column the weight of all the water above is resting on the bottom of the column, this weight creates pressure.
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Old 05-12-2021, 07:31 PM   #9
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Old 05-12-2021, 10:59 PM   #10
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Does that formula work for water? I thing PV=nRT only applies only to gases?

What Morich is describing is PE as in potential energy. As in mass and affects of gravity.
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