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Old 29-12-2009, 14:33   #1
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Crazy Pressure-Water Problem!

Hi all;

I am having a very odd issue with our pressure water system. The problem is that we have water pressure at the hot water tank, but no cold water making it's way to the faucets. Here is the rundown....

Installed a Jabso water pump, one of those new fangled units that don't need an accumulator tank, and can vary pump speed as demand changes. Worked fine for months. Then, I replaced the hot water tank. It is a Webasto wall mount unit, that heats from AC or engine. Once this was installed, the pump would not shut off on it's own, and the how water was making it's way out of the tank and back down to the cold water line to the faucets. We only had hot water.

The solution was to install a check valve in the line supplying the hot water tank, so that the hot water could not come back out of the tank down the supply line and feed the sink faucet. This worked, but, now we cannot get any cold water out of either faucet.

If the pressure in the hot tank is low enough to call for pressure, and the cold water faucet is open, we will get cold water until the hot water tanks is charged, and then no more.


Here is how it is plumbed. Output of pump goes to a T connector. One end of that goes to the hot water thank (with the check valve installed) and the other end goes forward through the bulkhead, to another t connector. One end of this goes to each sink cold side on the boat.

I removed the hose from the pump discharge end, and was able to blow water out of the open cold faucet.

So, is this a problem with the pressure switch on the pump, an internal pump issue, or ??? I am stumped.

Chris
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Old 29-12-2009, 14:39   #2
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Have you bled the feed line and both faucets? Open them both and make sure the hot tank is low enough to call for water. Make sure water flows through all hot and cold faucets as a solid stream, then close the hot sides. Does the cold still flow?
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Old 29-12-2009, 14:59   #3
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Christian;

Thanks for the quick reply. I Tried as you outlined, and water flowed as it should, but the pump would not shut off. It was building up the pressure in the hot water side much higher than normal, and then the breaker popped.

Chris
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Old 29-12-2009, 15:38   #4
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on most hot water heaters there is two "in,s" and two "out,s" if you have them the wrong way around ie both inlet and outlet comming from an "in" this would cause your problem ?if not perhaps the shutoff valve on the pump is faulty good luck andy
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Old 29-12-2009, 15:59   #5
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The heater certainly does have two inlets and two outlets. One set is for the engine heating coolant, so that certainly is not the issue. It is possible that I have the inlet and outlet for the fresh water reversed, that would cause the problem? how so?

I cannot check easily, as they are on the underside of the heater, which is bulkhead mounted fairly low. I cannot see the markings I could swap them in about 30 minutes, so maybe that is the best next step.

Chris
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Old 29-12-2009, 17:28   #6
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I would think the heater manual would have a picture or diagram of the in and out locations, if not I would call the service dept. and see if they could tell you which side is which. they might be able to give you some clues as to the problem as well. this is a new one on me but it does sound like you could have them backwards. That could cause an air lock that could cause problems. Let us know when you find the problem so we can learn from your suffering lol.

Good Luck
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Old 29-12-2009, 19:29   #7
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These electronic sensor pumps MUST have a battery in the feed circuit...they will not run directly off a battery charger. Do you have the house bank on?
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Old 29-12-2009, 22:34   #8
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Chris, I'm wondering if the hot water tank, because of its size, is simply able to absorb so much of the output power of the pump, that it is "eating" all of the pressure and the relatively higher constriction of the cold water line simply is restricting the flow of cold water.

Or, if there's an overpressure relief valve in the hot water tank (there should be) perhaps that is releasing, and, again, as a result the hot water tank is simply hogging all the output from the pump.

Have you asked Jabsco (I know, no one is answering phones this week) if that pump CAN pressurize a hot water tank of that capacity? You may need to upgrade the pump, or deal with the hot water pressure separately.
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Old 29-12-2009, 23:11   #9
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1. Is the checkvalve properly oriented

2. Call www.depcopump.com as for marine pumps
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Old 30-12-2009, 09:00   #10
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I have installed these pumps.

The first issue is that you need to find out why the hot water system is not pressurising and stopping the pump, You either have a leak or a faulty sensor. In other words, if you close the hot and cold faucets, the pump should stop normally, opeing and closing the hot one, should result in proper operation of the pump. The breaker should never pop. Get this working right first. Then look at the next step.
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