City water filling fresh tank

Wild Card - that's good to know. It kind of confirms that this pump design may be faulty. Or maybe they fixed it with their rebuild kit? Read on.

I tried installing an external check valve on the suction side - a $7 PVC model that I picked up at the chain home improvements store. That fixed the problem for about 48 hours, then THAT check valve failed. Kind of off-topic, but just a caution - don't try to fix such problems with irrigation check valves. Get something of higher quality.

So I broke down and got ShurFlo's check valve rebuild kit 94-800-03 for around 1/3 the price of a new pump. After 4 days of being hooked up to city water pressure (reduced to 40 psi by a pressure regulator), there is no backflow through the pump whatsoever.

Here's why I think there may be more to the rebuild kit than just replenishing worn springs and diaphragms; Included in the rebuild kit was the entire pressure switch housing. (reference assembly 5 on page 1 of the diagram at this link where it is referred to simply as "Pressure Sw. 94-800-05")

http://shurflo.com/images/files/RV_Product_Data_Sheets/Fresh_Water_Pumps/pds-4008-101-X65.pdf

Now this pressure switch housing has an electrical connection and it holds the diaphragm, spring, and plunger. What I alluded to at the top of this post is that this may be more than just a rebuild kit for worn out rubber pieces; the pressure switch housing may be a revised part which fixes a faulty design. Because the rebuild instructions enclosed in the kit package go into detail on how to remove all of the pieces from the existing pressure switch housing, and then replace them. The instructions do not indicate that a pressure switch housing assembly is included - they instruct you to rebuild the old one.

However, seeing that a new pressure switch housing is included in the kit, you simply take the old pressure switch housing off with three screws, throw it away, and then with the pieces included in the rebuild kit, insert the new plunger, spring, and diaphragm into the newly-supplied pressure switch housing assembly and screw it back on.

Look for me again at this same post if and when it fails, but it's holding tight now!

JJinVista wrote:
augustpilot, what brand / model of pump are we talking about?

I have a like-new pump, a Shurflo 4008 Revolution, and it's exhibiting the same problem with water flowing backward through the pump.

I've had it apart a couple of times now. I've identified the check valve which is located within the pump, and inspected the check valve seals, o-rings, and for signs of debris or grit. Nothing appears worn, defective or dirty.

I know water is flowing through the pump backward because I've disconnected the suction side of the pump (once it was primed), had the pressure side connected to city water and have seen it drip out the suction side at a rate of around 6 drops / sec.

What's odd is that it inconsistently does this.

If the pump isn't primed (as when I had it out of the RV, hooked to a garden hose on the pressure side), it doesn't fail / backflow.

With it hooked up in the RV and the pressure side of the pump pressurized with city water, it doesn't fail as long as it's not primed.

I ran the pump for a few seconds like this (dry), and it doesn't fail. (The manufacturer says this pump can be run dry without damage).

Only once the pump is connected to a water source on the supply / suction side, primed and a few cycles of turning a fixture on and off, causing the pump to cycle, will it then start to leak backwards from the pressurized side to the supply side.

This leaking condition persists, even when the city water supply / pressure is not present, and even after opening a fixture valve to take all pressure out of the system. Granted, the leaking condition would eventually stop when there's no more water in the plumbing lines to backflow, but it appears that simple gravity and / or siphoning action is making this happen.

I feel that maybe this particular design, brand or model pump is prone to this problem. Or else maybe there's a defect in this particular pump's housing so it doesn't matter what condition the o-rings and gaskets are in.

I'd like to hear from others as far as what brand / model pump has had this problem, the age of the pump at the time of the problem, and if a check valve rebuild kit fixed the problem.

Not sure I want to waste my time getting a check valve rebuild kit because even if it fixes the problem, it appears that this pump's check valve design can't tolerate much wear before the condition will begin again.

Maybe I'll just add an external secondary check valve, as the pump itself works great.

I have same pump and same problem. It's the next thing to go bye bye

I simply install a manual valve at city water to keep pressure of my pump & tank.Easy to turn then you know.

augustpilot, what brand / model of pump are we talking about?

I have a like-new pump, a Shurflo 4008 Revolution, and it's exhibiting the same problem with water flowing backward through the pump.

I've had it apart a couple of times now. I've identified the check valve which is located within the pump, and inspected the check valve seals, o-rings, and for signs of debris or grit. Nothing appears worn, defective or dirty.

I know water is flowing through the pump backward because I've disconnected the suction side of the pump (once it was primed), had the pressure side connected to city water and have seen it drip out the suction side at a rate of around 6 drops / sec.

What's odd is that it inconsistently does this.

If the pump isn't primed (as when I had it out of the RV, hooked to a garden hose on the pressure side), it doesn't fail / backflow.

With it hooked up in the RV and the pressure side of the pump pressurized with city water, it doesn't fail as long as it's not primed.

I ran the pump for a few seconds like this (dry), and it doesn't fail. (The manufacturer says this pump can be run dry without damage).

Only once the pump is connected to a water source on the supply / suction side, primed and a few cycles of turning a fixture on and off, causing the pump to cycle, will it then start to leak backwards from the pressurized side to the supply side.

This leaking condition persists, even when the city water supply / pressure is not present, and even after opening a fixture valve to take all pressure out of the system. Granted, the leaking condition would eventually stop when there's no more water in the plumbing lines to backflow, but it appears that simple gravity and / or siphoning action is making this happen.

I feel that maybe this particular design, brand or model pump is prone to this problem. Or else maybe there's a defect in this particular pump's housing so it doesn't matter what condition the o-rings and gaskets are in.

I'd like to hear from others as far as what brand / model pump has had this problem, the age of the pump at the time of the problem, and if a check valve rebuild kit fixed the problem.

Not sure I want to waste my time getting a check valve rebuild kit because even if it fixes the problem, it appears that this pump's check valve design can't tolerate much wear before the condition will begin again.

Maybe I'll just add an external secondary check valve, as the pump itself works great.

You have a bad check valve

augustpilot wrote:
Thanks everyone for all responses. I turned off city water, turned on water pump and ran until tank was empty. Then turned on city water , everything normal, the tank has not refilled via pump. My water tank gravity fills from side of coach. Then water is pumped from tank with water pump. Only way water got back to,tank was through the pump. The valve seemed to have reset in pump and now working ok.

Dont get to comfortable that its fixed. Mine has done it since 6mo old. Slowly filling tank when on city water. I had a 1/3 tank last Thursday night when hooked at campground, had 3/4 tank Monday morning when I disconected. Just monitor it is all I am saying.

augustpilot wrote:
Thanks everyone for all responses. I turned off city water, turned on water pump and ran until tank was empty. Then turned on city water , everything normal, the tank has not refilled via pump. My water tank gravity fills from side of coach. Then water is pumped from tank with water pump. Only way water got back to,tank was through the pump. The valve seemed to have reset in pump and now working ok.

Probably had some debris in the check valve.

Thanks everyone for all responses. I turned off city water, turned on water pump and ran until tank was empty. Then turned on city water , everything normal, the tank has not refilled via pump. My water tank gravity fills from side of coach. Then water is pumped from tank with water pump. Only way water got back to,tank was through the pump. The valve seemed to have reset in pump and now working ok.

Pump has a checkvalve that is leaking by. Take suction line off pump and connect city water and watch the results. Replace pump

wnjj wrote:

Farmboy666 wrote:
I did answer where the valve is, it’s on the line going into the tank. I only have one line going into and out of the tank. It has a ball valve, when I want to fill it I hook up a hose and fill it, when it’s full I unhook or turn off the city water an it gravity feeds out of my tank to the pump. If I want to use city water I close the valve to the tank to stop it from filling and use city water pressure. That about as plainly as I can explain. One line to my tank with a ball valve.

One more try and then I give up. One line and a ball valve doesn’t explain it enough. Where is the pump connected? Obviously the pressure side of the pump connects to the pressure side of the system but where does it get it’s input? From a tee in the line with the ball valve? On the tank side or other side of the ball valve on that line? Directly from the tank (though you said there’s only one line in/out)?

Simply saying there’s a line from the city water inlet to a ball valve to the tank doesn’t leave any more fittings to connect anything to. At a minimum I’m assuming the city inlet has a tee that goes to the pressure side of the system and to one side of the ball valve.

Forgetting filling the tank for the moment and consider this: If you can switch between city water and using the pump without moving any valves, then your pump is in between the pressure side and the tank and CAN leak back if it fails.

The reason I’m pressing this is it appears your RV is different than every one I’ve ever seen described, uses less parts and is apparently immune to pump check valve failure. If so this would be a nice upgrade to these standard systems.

The standard systems have 2 different paths between the pressure side (city inlet) and the tank. One is the pump. The other is a piped connection with the fill valve in line. They are in parallel. So if you open the fill valve city water fills the tank (and the pump would just circulate water back into the tank if you tried to run it this way). With the valve closed, the pump OR the city inlet can build pressure, but that pressure can leak back through a bad pump. RV’s without a fill valve just have a graviy fill that connects directly to the tank. As a cheat on some of those you can poke the outside shower hose back into the gravity fill and now your shower valve becomes a fill valve.

Hopefully this discussion helps the OP to understand and locate his issue.

I guess I assumed that it was obvious there is a tee in the line. I also assumed that when I say I open the ball valve and it gravity feeds to the pump that you can figure out where the pump gets it's feed from. I don't know how else to explain it and I know it works. My original statement was if the check valve in the pump fails it cannot fill my tank because it's either already getting the water from the tank or the ball valve is closed and I'm on city water. I know plumbing can be hard to explain or understand sometimes. I have been building houses for 40+ years and started plumbing in the 70's so I have some experience. RV plumbing can be complicated and maybe the guy who plumbed mine was either having a good day or a bad day since it looks like I'm the only person in the US who has this system. Either way that's what I have and like you I'm giving up. Happy camping