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Post by renegade27 on May 9, 2015 14:38:33 GMT
Hi, all! Happy spring to the Northern Hemisphere... enjoy! I know I will be with my favorite toy, a 2006 JSO 35...
I'm getting my boat back into use shape - - filled the water tanks (well, not filled completely) and I noticed a lot more weaker water flow when I select the aft tank. Water from the forward tank seems perfect as expected.
After the pump fills pressure in the aft, I can only run water for a minute or two (normal flow) before the stream becomes weak even with the pump pulling. Another minute or two and I'm getting almost nothing from the tank.
Bilge is dry, dry, dry. All the filters (which are shared with the forward tank without problem) are cleaned out.
I suspect air leakage, but don't seem to get the pump cycling much (or at all) with the faucets closed. I looked at the manual, and there appears to be only two connections - one on either side of a single hose connecting the tank to the selection valve. I will check these with soap bubbles, but wouldn't the pump cycle on if these were leaking?
This engineer is stumped. Ideas?
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Post by amathus on May 9, 2015 16:00:36 GMT
Have you got an airlock (as opposed to an air leak) in the aft tank delivery piping? It can happen when you let a tank run dry then switch to your other tank to repressurise the system. You may have tried this, especially if you have an engineer looking but I would do the following before any other solution are sought.
Open both of the tank valves. Make sure that you have the correct pressure in the expansion vessel ( because this is what keeps the pressure in the system and can be a reason for a stronger flow from a nearer tank). You can top up with just a bicycle pump. The manual will tell you how much and there should be a label on the tank. I suspect it is a Jabsco one give the year of the boat and the Internet can also be a source of information.
Once you are all set up run ALL taps on full including the transom shower. Listen/look for any air or splurges in the running. If you hear or see that then it is good news because it's getting the air out of the system. Once all taps have reached full flow then keep them running for about a minute and the pump has had a jolly good run turn off taps and shower and close the front tank valve. Try it now, from the rear tank and see if the thing has fixed itself. If not then try a little higher pressure to the expansion tank but not too higher than recommended. Too much in there will also affect the performance of the system.
Hope this helps
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Post by MalcolmP on May 9, 2015 17:32:12 GMT
Probably unlikely, but the tank needs to be able to draw air in to avoid a vacuum occurring. Unlikely I know but maybe check that the breather pipe has not been flattened or blocked in some way
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Post by amathus on May 9, 2015 17:53:55 GMT
Can test that theory by just running the water then opening the filler cap.
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Post by renegade27 on May 10, 2015 15:30:52 GMT
2 great suggestions! Thank you both! I *have* an engineer looking at them, but its only me and the engineer didn't think of these.  I will give each a try this week when I go back up to the boat. |
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Post by windward54 on May 11, 2015 1:50:33 GMT
We had a similar problem on our boat. After filling the aft tank, we could only draw about 4 or 5 liters before we were sucking more air than water. Turned out that the draw tube had a hairline crack where the tube met the fitting. Most likely it was a bad soldering job when manufactured. I got a whole new tube assembly from Jeanneau, and all was fine.
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Post by renegade27 on May 11, 2015 12:02:54 GMT
Windward, which is the 'draw tube'? and which fitting did you check?
(I believe) there are 3 tubes attached to the tank - the fill tube, the tube connecting the tank to the pump and supply (both visible) and then a tube that connects to the vent (? I haven't found that yet but maybe if I start unscrewing boards in the back berth).
Was it the fitting on the tank or the fitting by the switches leading to the filter and then pump?
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Post by windward54 on May 11, 2015 14:31:51 GMT
The draw or pick up tube (or at least that's what I was taught to call it!) is the tube that extends from the top of the tank to the bottom. On top of the water tank there should be a fitting where the water hose connects to the tank, and draws the water out of the tank and into the water system for use. Attached to this fitting inside the tank should be a tube that extends to the base of the tank. This is so when the system pressurizes, the water is drawn from the bottom of the tank, and an air vent allows air in to replace the volume of water. If there is a leak anywhere on the tube, the system will suck air and not water.
On our aft tank, the tube had a bad weld to the fitting, and had a hairline crack where the two met. When completely full, the water level in the tank was sufficient to cover the crack, and I could pull some water. After just a few liters, the crack would be above the water level and I would start to pull more air than water. After a few more liters, I was just pulling air. It's kind of like trying to use a straw with a hole in it to suck water from glass. you'll get some water to start, but eventually you can't get enough of a pressure differential to get any water up the straw.
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