City water pressure July 16, 2009, 09:59:47 pm Yahoo Message Number: 103941During a recent Escapee Escapade, I attended a session on the RV fresh water system. The speaker, who seemed very knowledgeable, said the components used in RV fresh water systems are rated at 125# pressure. He went on to say that your typical RV manufacturer pressure tests the system at around 100#. I e-mailed Steve at LD about the pressure test they do and he said they use pressurized air in the 80# to 85# range. The Escapee speaker went on to say that even with a 100# test of a 125# system, or 80-85# test by LD, RV manufactures then recommend the use of a pressure regulator set at 40# pressure when on city water. LD makes this recommendation as well. He said, only half cynically, the only reason they do this is to minimize warranty claims. The result of the 40# is unnecessarily poor water pressure throughout the entire system when on city water. I's my experience that the Shurflo Extreme 5.7 pump puts out a pressure much higher than the city water regulated 40#; the shower is much more satisfying, the toilet flushes better, the sink spray is stronger, etc. The Shurflo 5.7 Owners Manual says "The pump shut-off pressure is 65#. The system must be designed to handle 65#" I suspect the pump is operating in the 60# range but have no way to measure the pressure. I use an adjustable water pressure regulator. It's been set at 50# for over a month. Even at 50# the water pressure is not as good as the pump. When we use the shower, if we're on city water, I shut off the city water and use the pump for the shower. It gives a much better shower. Next time I'm on city water, I'm going to 55# if the water pressure is sufficient. If nothing starts to leak, my goal is 60# which is less than 50% of the system components maximum of 125#, 75% of the LD 80# test and 5# less then the Shurflo requirement of a 65# system. Tired of the wimpy 40# water pressure.Any ideas how I might measure the pump pressure?Ed
Re: City water pressure Reply #1 – July 16, 2009, 10:44:54 pm Yahoo Message Number: 103942Ed, There are 2 factors that need to be considered, you are only looking at one, water pressure. The second is flow rate or GPM (gallons per minute). I would suspect that this is where the real issue is when comparing the two. Lets look at the path the water takes when using your internal pump. It flows from the tank through the pump and through plumping and exits the faucet. Ok, fairly simple. Now, from the city water. Water spigot, water hose, maybe a filter, pressure regulator then through the city water inlet, then the rest is the same. I'm sure you have looked closely at the city inlet and pressure regulator, they are not exactly open orifices. There is a lot of restriction to flow. Thus cutting back on the available GPM.I'm trying to think of a good example to explain this better, but nothing comes to mind. Oh, let's look at a air compressors. (Water and air behave very much the same in this example. You can buy a little portable unit that is capable of 150 psi, but it will take a lot longer to fill a tire than one with a large reserve tank. Why, CFM (cubic feet per minute). The pressure can be the same, but the flow is much greater with the tank unit.Here is another way to look at it. You have a 1/2" diameter water hose pressurized to 100#. It then goes to a tank that has a 1" diameter spigot at the bottom. When I first open the spigot I will have 100# for just a moment, then it will start dropping. If I left the spigot open long enough, I will eventually drain the tank and I will only get what lever flow rate the 1/2" hose can deliver. The pressure will end up being very low, but the flow rate will be the same. So, my therory is, you will not be able to equal the flow rate as long as those restrictions are there. Hopefully I make sense, or someone else can maybe explain it better.Hope this helps,-Victor
Re: City water pressure Reply #2 – July 16, 2009, 11:23:14 pm Yahoo Message Number: 103944Victor brings up a very important point: both pressure and flow rate contribute to your showering experience, and it's well known that the pressure regulators sold to RVers significantly restrict the flow rate. I'd bet on that, rather than pressure, as the main reason for the symptoms you describe. It's easy to say "Aw, they're just covering their asses by saying 40 psi," but even modern plumbing systems do lose strength gradually as they age. For that matter, older RVs like my 1985 were built with different plumbing materials that were much more prone to failure. If you'd ever experienced a burst pipe in a Lazy Daze--as some people here have--you might be less eager to subject your system to higher-than-recommended pressures. (Not to mention that if anybody at Lazy Daze reads your last message, your warranty is out the window. ;-) I believe at least one person here (Larry Wade? Bumper?) has come up with a way to use a larger, higher-flow regulator, with some plumbing adapters on either end, to maximize the flow rate while still safely limiting the pressure. That approach might satisfy your craving for more water in the shower without risking a catastrophic plumbing failure.Andy Baird http://www.andybaird.com/travels/
Re: City water pressure Reply #3 – July 17, 2009, 09:53:43 am Yahoo Message Number: 103946When I checked the regulator provided by Lazy Daze and another that I had purchased, they actually had an output pressure of 50 psi.I agree with the comments about flow rate.Linley
Re: City water pressure Reply #4 – July 17, 2009, 12:41:15 pm Yahoo Message Number: 103947Quote Any ideas how I might measure the pump pressure?Ed Reading the replies I'm impressed, as always, with the expertise in this group. The comments make sense to me. I should note that my lengthy showers are always satisfying, with good pressure and flow, and I never have to worry about filling the grey water tank.See you at the bathhouse. :-)Paul NE 50
Re: City water pressure Reply #5 – July 17, 2009, 04:42:15 pm Yahoo Message Number: 103950Quote Ed, There are 2 factors that need to be considered, you are only looking at one, water pressure. The second is flow rate or GPM (gallons per minute). I would suspect that this is where the real issue is when comparing the two. Thanks Victor. I did forget to factor in the flow rate. The pump is the 5.7 series which means it's capable of a flow rate of 5.7 gpm. My filter is designed for a flow rate of 4 gpm. No way to change those numbers. Guess I'll continue what I typically do. Fill the tank through the filter then simply run off the tank.Thanks:Ed
Re: City water pressure Reply #6 – July 17, 2009, 05:43:29 pm Yahoo Message Number: 103951Quote It's easy to say "Aw, they're just covering their asses by saying 40 psi," but even modern plumbing systems do lose strength gradually as they age. Appreciate your concern, Andy but given a 2008 LD, with 125# components, tested at 80 to 85#, with a pump that requires the manufacturer to build a plumbing system that can handle 65# I feel perfectly comfortable at a pressure in the 55 to 60# range. I suspect the pump is operating in this pressure range now. Warranty: The LD warranty on systems like plumbing is limited to one year from the date of delivery. I'm out of that range.Take care:Ed2008 MB15 months & 27,000 miles later. Having the time of our life.
Re: City water pressure Reply #7 – July 18, 2009, 03:10:03 pm Yahoo Message Number: 103969Ed,I am not a plumber. I would not suggest you go over 40#. Plumbing parts, RV or residential are not designed for higher pressures. Failure may not come quickly, but expect it to happen if you exceed the design pressure. I would suggest you continue to run off the pump to get a decent flow of water. We never connect to city water.Cheers, Don
Re: City water pressure Reply #8 – July 18, 2009, 09:13:26 pm Yahoo Message Number: 103997It's interesting, Don. Went
Re: City water pressure Reply #9 – July 20, 2009, 10:50:38 am Yahoo Message Number: 104023Quote It's interesting, Don. Went in Wal-Mart today for some stuff. While there, I looked at the pressure regulators they sell in the RV area. The container says the regulators are calibrated somewhere between 40# and 50#. After I discovered that the pressures were running high, I examined the constructioin of the regulator. Expermenting, I used a long pin punch and reached down into the regulator with it. A few taps of a hammer reset the pressure to 40 psi.Linley
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