JJinVista
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Re: 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!479Views0likes0CommentsRe: City water filling fresh tank
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.479Views0likes0Comments
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