Water tank pick up

[Rjm st.petersburg]

When I open the galley faucet initially it comes out with plenty of pressure and volume. Then both pressure and volume dwindle down after about 30 second's. The pump will stay running. After I shut off the faucet eventually, a couple of minutes, there will be enough pressure to shut the pump down. This happens at all of the faucets.
When I disconnected the blue water line at the top of the tank and put it in a bucket of water it ran fine. The pump had enough water volume and pressure to allow it to actually cycle, without a loss of pressure or volume.
The bucket just took the place of a tank. That is why I am focusing on the tank.

 

[Steve_Catalina]

I haven't tried that because when I put the pick up side in a bucket of water it ran fine on both sides.

OK, then the pump by your test seems good. Prior to the intake side of your pump where do the two tanks come together? Since both tanks have an issue, just work back from the pump inlet to the common point of the tanks.

Did some of 10 pounds of caulk get into one of the tanks and flow into common piping they share?

 

[Rjm st.petersburg]

They come together at the pump, with individual cut offs. I tried one tank at a time, with no improvement. The 10 lbs of caulk could have gotten into the port tank, but not the starboard tank. Each line at the tank to the pump tested good.

 

[DayDreamer41]

They come together at the pump, with individual cut offs. I tried one tank at a time, with no improvement. The 10 lbs of caulk could have gotten into the port tank, but not the starboard tank. Each line at the tank to the pump tested good.

It doesn't sound like you have anything in the lines if I am reading your test correctly you took each suction line off the top of the tank and put it in a bucket and all was good, which would indicated that the lines are clear from the top of the tanks to the pump. What doesn't add up is if the port tank suction line in the tank was clogged it should work fine from pulling from the starboard tank, very interesting problem.
I know a couple of years ago when commissioning the spring I had the starboard tank line connection was not seated and it was pulling air which prevented the pump from priming, seated the line and all was fine. It almost sound like you have an issue with both pickup lines in the tanks, I would be interested in what you find that is for certain.

 

[Tally Ho]

It “acts” like a plugged vent or something similar, since you say it starts out strong, but dies out (pretty quickly).

But you said you opened the fill caps, and it still did the same thing, so I wouldn’t guess a vacuum. But it seems like it acts like that.

On my JD tractor, I could run it about 30 minutes, and then the engine would die out (starved for fuel). I went straight to the fuel filter…pulled off one hose, and heard gas flowing “back” into the tank…basically released the vacuum that was being pulled because the tank vent was plugged up with dirt…after about 30 minutes, the fuel pump could not overcome the vacuum and the engine would die.

Your problem is equally a mystery…and then you will figure it out and say “why the heck didn’t I see that sooner”!


Greg

 

[Rjm st.petersburg]

It is quite puzzling. Each line from the tank to the pump, tests good. When the opening of the deck fill caps was suggested, I thought that would be the answer, clogged vent lines, I was wrong. I tried slowly puring water over the connections to see if I could detect a suction leak, to no avail. My gut is saying it's a crack in the pick up above the water level just inside of the tank. However it's in both tanks. That's why I suspected it might have froze with water in the pickup. The P.O. hasn't gotten back to me about that possibility.

 

[Ward H]

When you tested the blue lines by putting them in a bucket, did you do one tank at a time?
When you have the issue do you have both tanks supply valves open?
Have you tried just one tank at a time?

I ask because I have read that you should only have one tank supply open at a time so the pump works properly. Never understood why, as my tanks have bottom mounted outlets. Head pressure pushes the water to the pump so with both tank supplies open there is double the head pressure.
But, with your outlets at the top of the tank and having to have pick up tubes, your pump must be capable of lifting the water up and out of the tanks.
When using both tanks does that double the "lift" required by the pump to get enough water supply?

 

[Rjm st.petersburg]

I tried one at a time and both together, no difference.

 

[Slipin Away]

Sounds like you might have a screen on the pickup tube that is clogged. Might try removing the blue line and use a stiff wire put in the fitting and see if it is clear without removing the fitting

 

[Davidasailor26]

What is the height of the bucket when you’re doing that test? Are you keeping the top of the water in the bucket at about the same height as the water level in the tank, or sitting it up higher? If the bucket is higher it might be siphoning itself into the pump and overcoming any leaks along the way, which the lower water level in the tank couldn’t do.

 

[Rjm st.petersburg]

Great point. The bottom of the bucket where the hose line was, about 2" higher than it would have been connected to the tank.
Once pressure is achieved, it holds it pretty well so long as there isn't any usage. So overnight with the pump switch off, there will be pressure the next day. I haven't noticed my tanks draining down, or water in my bilge.

 

[Rjm st.petersburg]

Sounds like you might have a screen on the pickup tube that is clogged. Might try removing the blue line and use a stiff wire put in the fitting and see if it is clear without removing the fitting

I did blow compressed air through the fitting into the tank. I had bailing wire with me, but I couldn't get it passed the 90 degree elbow fitting. I'll try some copper #6 or stranded copper #12 today.

 

[DayDreamer41]

In thinking of what could possibly be wrong I am truly bewildered, if it was (2) broken pickup tubes then you would pull air and get a gurgling sound when the pump was running as it would be pulling air, if they were completely broken the pump would never prime, if either of the lines from the tanks wasn't sealed you would be pulling air, and yet when pulling water from a bucket the system works. Simply baffling......
The only thing that comes to mind is the pickup tubes on both tanks are collapsing pinching off flow as the suction pressure rises.
Does the top of the starboard tank look like its been modified at all? Just wondering what the OP did, in your picture of the Port tank I don't see any of the expanded foam which Hunter put in between the tanks and the liner supports to hold the tank in place, just wondering if the tanks had been changed out along the way.
If you can't get the fitting undone on the supply/suction line you may have to cut it out and patch the tank replacing the fitting and pickup tube, its unfortunate that this kind of crap is passed down to the next owner, I sure hope the OP get back to you with some kind of explanation.

 

[Rjm st.petersburg]

I think it's very strange as well, especially since it's both tanks.
I will try running a wire through the fitting again.
Then I will fill the tank until the water comes out of the vent tube and also spills onto the deck. Let it continue to overfill while I run the pump.
If that works, than I probably have a crack in the pickup tube.

 

[DayDreamer41]

If you can't get the fitting undone on the supply/suction line you may have to cut it out and patch the tank replacing the fitting and pickup tube, its unfortunate that this kind of crap is passed down to the next owner, I sure hope the OP get back to you with some kind of explanation. I have my doubts though given the debotchery on the top of the port tank.....

 

[JamesG161]

After reading the entire post and all your tests, the only thing in common is..

The Pump and its suction strainer and that single suction line.

The fact of pumping out of a bucket is the Confusion.
_____

You are LIFTING water with the pump from your tanks.

As the level in a tank drops, the LIFT increases.

Since you empty your tanks, no lift pipe issue.

If you can provide a picture of the pump and input line, we might be able to tell you more.

My best guess...
You need a new Pump.

Jim...

 

[Rjm st.petersburg]

I thought about abandoning and plugging the fitting as well.
Tally Ho installed a nice clean out port in his tank.
The P.O. has responded to other questions I had, but I doubt he will on this one. Ultimately my gripe is with the surveyor who was supposed to be working for me, since I paid him. They were recommended by our broker, who was friends with my girlfriend. So much for friendship.

 

[Rjm st.petersburg]

It is a brand new pump, with a new strainer, and new filter.

 

[DayDreamer41]

After reading the entire post and all your tests, the only thing in common is..

The Pump and its suction strainer and that single suction line.

The fact of pumping out of a bucket is the Confusion.
_____

You are LIFTING water with the pump from your tanks.

As the level in a tank drops, the LIFT increases.

Since you empty your tanks, no lift pipe issue.

If you can provide a picture of the pump and input line, we might be able to tell you more.

My best guess...
You need a new Pump.

Jim...

The pump is here under the galley sink Modifying the Galley Sink Drain Pipe - 41DS

 

[Rjm st.petersburg]

Yes that is correct. 2 blue lines feed into cutoffs, then combine into 1 blue line to supply the pump. I tried 1 at a time, and both together.
Since it works from where it connects to the tank, I'm pretty sure it's something with the pickup. I would stake my ex-wife on it.