Weird Water Pump Behavior Resolved But Cause Unknown

BrianZ

While preparing the trailer for a trip without hookups, I filled all the plumbing via city water port, flushed out all air, then added water to the fresh water tank to 40% level for testing the pump.  The pump ran, but wouldn't stop & would not reach full pressure, even after several minutes.  I immediately checked everywhere I could think of for leaks, but found none, including the valve area, mixing valve, all reachable fittings behind toilet, & under trailer.  I could open the fresh water tank drain valve & get water.  Checked all valve settings - they were in the correct position.  I checked the pump filter - clean; removed the pump input hose & was able to blow air into the fresh water tank without resistance; then removed the output hose & attached a short piece of hose & was able to pump water into a jug.  Reconnected pump hose, and turned pump back on.  Within about 10 seconds, the pump achieved full pressure and stopped.  Everything was back to normal, but I have no idea what the problem was.
Any ideas?

Sharon_is_SAM

This should not matter, but do you think because the system was pressurized by the city water, the pump was working against that pressure?  When you disconnect the hose from the city water connection, if you stick your finger in to open the check valve, there is a lot of pressure that is relieved.

BrianZ

Makes sense, except that I had opened faucets to see if there was any pressure & water flowed out, but not very strong, getting weaker & weaker until no more flowed.  Pump still didn't pressurize until after I disconnected pump hoses etc.  It was weird, but glad it finally worked.

ChanW

Brian, that's happened to me, and I've figured it was just an air 'cushion' that needed to be purged from the lines, or maybe it's an 'airlock' of some sort, in the pump itself.

lkc001

@BrianZ I have had the exact same thing happen to me.  This is what I ended up with as an answer for myself.  Whether it is correct, remains to be seen and listen to me at your own risk--haha!   So you say you filled/pressurized the system from city water--did you fill the hot water tank also by opening the hot water faucet & letting it run until it stopped sputtering while you were still on city water?  Then you unhooked the city water & filled the FW tank with a hose?   When this happened to me my pump kept running, but it was not making as much noise as when it was really pumping water--it was about half as noisy.  When I had your issue I had NOT hooked up to city water, I had filled my FW tank and ran faucets to get water thru the system.  However, I don't think my hot water tank was really full, so when I turned the pump off & it still kept running, I think it was still slowly trying to finish filling the hot water tank.  So then I turned on the pump switch again & the HW faucet open & let it run, turning pump & faucet off @ every 15 seconds.  Finally the pump stopped running when I shut off the HW faucet.  The next day I experimented by filling/pressurizing the lines on city water & filled the HW tank while hooked up to city water, THEN unhooked city water & filled FW tank with a hose and have never had that problem since.  Again, I think if you are trying to completely fill your HW tank from pumping it from the FW tank it slow filling the tank & it continues to try to fill the tank on a trickle.   It was weird, but like I said I have not had it happen since.  

BrianZ

Thanks for your reply, @lkc001.
To answer you 2 questions, yes and yes.
And the pump noise was continuously at the normal starting sound as long as I let it run - it never increased in noise as it normally does just before it stops.  However, it did stop running when I switched it off.  I did make sure air was out of the system by letting the sputtering stop for both hot & cold.  Hot side generally has more sputtering & takes longer to clear air.
Don't know if I have ever filled the lines via pump only.

lkc001

Yea, it's a mystery. . . . . which begs the question, if you're boondocking, as you use water from the HW tank, as long as the pump is on & HW faucet is open the system will be pulling water from the FW tank into the HW tank simultaneously??

BrianZ

Correct. Well, it's pushing water into the cold water lines which includes the feed to the hot water tank.  What exits the hot tank goes through the mixing valve, also fed by cold water & out to the hot water faucets.

BrianZ

Followup:

We went boondocking for a few days after this episode, and we had no problems at all with the pump.  This was our 12th camping trip in the 20 months we've had our T@B, and it was our first time without a shower facility in the park.  As a result, we tried out our shower for the first time, and we were both thankful for having it available. 

The shower worked fine & no problems having hot water available.  Despite trying to be conservative with water, I still managed to use about 4 gallons I estimated from the change in percentage on the SeeLevel meter plus tank capacity.  Would have been nice to have a fan, though the one ceiling helped; and cleaning up afterwards only required a couple of small towels to wipe everything down.  Because we didn't fill our tank all the way on arrival, we ended up taking our 6-gal jug in the car to get a refill, and used a drill-powered pump with short hoses to add it to the tank.

Ratkity

I love my drill-powered pump! I had gotten a cheap one locally and found a better one online. Verna taught me early on that a shower squeegee is a must! That, and a microfiber towel that dries quickly. to V!

4ncar

@ScottG even when there is a shower house, I still use my t@b shower🤷🏻‍♂️ That’s why I got it! Lol. Gloria on the other hand...uses the “full size”...