Dear Dave,
With all of the faucets in our rig (hot or cold), I turn one on and at first water rushes out at full pressure then quickly the stream reduces to a trickle. Then, just as fast, the flow is normal again. I have replaced the fixed pressure regulator and also my adjustable one with no change. As long as I continue to have good flow after a few seconds I’m not too worried, but I’d be curious to know what the cause is. I have not cleaned or changed the check valve at the city water inlet yet. Do you have any idea what this is caused by? Thanks in advance! —Drew, ’08 Winnebago Sightseer 35J
I received that question from Drew and asked him the following:
Drew,
This is happening when you are connected to city water, correct? Have you tried it at any other location to verify if it is an issue with the campground source or the rig itself? Are you using a filter on the incoming hose? I would suggest trying another location and if it still has the issue, change the check valve.
Drew responded:
It happens at all RV sites.
Then he provided more information:
Dave,
I wrote you about a water pressure problem and I need to clarify something. The pressure issue happens only with the hot water side (not both), as I said originally. Thanks. —Drew
Hi, Drew,
This is important information as it should eliminate the check valve on the city water valve; otherwise, it would happen on both hot and cold. Notice I said “should,” as I’ve learned never to say never or always when it comes to RVs!
Normally, I love it when I get a Winnebago question as I can go to the website and pull up a 3D drawing. It’s almost like being there. Unfortunately, the documentation in 2008 was not what it is today, although I’m sure it was the best at the time. Here is what was available on the site for your model.
It is hard to see; however, there are no check valves or anti-syphon devices that would cause any type of water flow issue before or after the water heater. Some models had an accumulator tank that was a bladder holding water to add pressure to the system. However, I do not see that in the diagram or in the specifications. So, it must be an issue with either the supply line coming into the water heater, or one coming out.
Water heater pressure relief valve
Your water heater has a pressure relief valve that is visible from the outside of the rig by opening the vent door.
This is an Atwood model used on a 2003 Winnebago Brave with the pressure relief valve located to the left of the module board. This could be weak or clogged with calcium, rust, or lime, and initially opening as you release pressure in a faucet. Go outside and open the vent cover to visually inspect what is happening to the valve when a faucet is open. If it is hissing or spraying out a mist, replace the valve.
As I have said many times, RVs have gremlins living in them that pop up at unusual times. Since this is only on the hot water side of the plumbing system, it could be a collapse of an incoming or outgoing water supply line that is weak. Most likely it is the outgoing, as the sudden rush of hot water may cause the pipe to initially collapse, restricting water flow until it adjusts to the temperature. It could also be a clogged pipe with sediment that restricts the flow initially. However, that would typically be a one-time issue. But, as I stated earlier, never say never!
Inspect the lines coming to and from the water heater and watch what is happening. An initial “jump” or flexing would indicate a restriction and might help isolate the problem. It should be easy to replace a section of piping with new PEX lines and compression fittings.
You might also enjoy this from Dave
Cold water runs in a trickle, but hot water runs fine. What gives?
Dear Dave,
Our cold RV water pressure at the kitchen sink is a trickle, both on city water and using our pump. The hot water pressure is fine. The shower and bathroom cold and hot water pressure are fine. What could be causing this problem? When we first purchased (new), the kitchen cold water pressure was tolerable but has steadily gotten worse over the years. Yes, we’ve cleaned out the faucet screen numerous times, which doesn’t account for the hot water flow being fine. —Chris, 2015 Nexus Viper 27
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Hey Dave
Thats a real strange one with several possible issues that Dave mentioned. I was thinking that maybe draining & flushing the hot water tank might help. Perhaps Drew could send in a pic of his exact water heater, In the diagram that Dave shows is from a 2003 Atwood water heater not the 2008 one that Drew has, might be different?
Thanks
Snoopy
Thank you, Dave! At the very least you ensured that Drew has a diagram of the waterlines in his RV. More likely, you also got him closer to discovering the source of his problem, if not give him the answer to it. Safe travels! 🙂
Dave,
Thank you for your detailed answer! I’ll try those things. I know already that I have a weeping high pressure valve and I’ll re establish the air gap to fix that. It also needs flushing. When I fix this I’ll let you know what I found. Thanks again, Drew
Like you said Dave, just the hot side adds to the mystery. I have seen a similar activity with the hot side of our shower and have to readjust the mix. My best guess is some component in the hot valve is expanding as the hot water finally gets to that side. Once hot water is steady, and I have readjusted the valve, there are no more changes.
I also see the phenomenon on all faucets hot and cold, and suspect the city water check valve traps higher pressure inside the system, while the park’s side has dropped in pressure. I get an initial burst then a more steady flow when I open a valve. My pressure gauge at the tap shows the park’s water system varies by about 10psi across the day.
My suggestion would be to flush the water heater really well, inspect the anode if it uses one. I suspect there is some large junk of debris in the hot water heater. What is occurring possibly is that debris whatever it might be, is being carried by the initial high flow of water to block the outlet of the water heater, the debris then falls away when the water flow slows, causing a good flow again, then a low flow situation again. Pressurized water lines usually do not collapse, but they can develop internal flapper valves depending on the material, when the inner liner if having one starts to deteriorate inside and it will never be seen externally.
Check the inlet side of the hot water heater. Had this happen to me, you have to disconnect the water line then unscrew the fitting that is on the heater, (I needed an impact to do that) should be a check valve there to keep hot water from going the wrong way. If it broke it will restrict cold water from entering the heater, and by turning off the faucet, pressure will come back but only for a spurt, then back to a trickle, if any. One more spare part I now carry.