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10-01-2018, 07:42
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#1
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Registered User
Join Date: Aug 2017
Location: Langkawi
Boat: Lagoon 450F
Posts: 4
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Lagoon 450 water pressure pump will not prime when switched over to other tanks
The port hull fresh water tanks are exhausted and have switched stopcock in port cupboard to starboard supply.
Jabsco water pressure pump will not prime?
Presume there is an airlock, any suggestions?
Are there any in line water filters standard?
(Have taken the cap off starboard tanks, there are full)
Any suggestions?
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10-01-2018, 07:56
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#2
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Registered User
Join Date: Mar 2007
Location: Santa Cruz
Boat: SAnta Cruz 27
Posts: 7,198
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Re: Lagoon 450 water pressure pump will not prime when switched over to other tanks
I assume you left one of the water taps open full, to reduce pressure in the system. If so the next step would be to suck on the tap while the pump is on.
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10-01-2018, 08:45
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#3
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Registered User
Join Date: Mar 2014
Location: Oz
Posts: 1,042
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Re: Lagoon 450 water pressure pump will not prime when switched over to other tanks
Switch all taps off. Open faucet on cold in port rear bathroom. Turn on pump. Let it run for about 1 minute - you should get hissing and spitting of water and will then come good.. If still no good, could be clogged strainer or it could be an air leak in the system. We had similar problem and found the in line water strainer at the pump had a crack in the lid.
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10-01-2018, 09:21
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#4
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Moderator
Join Date: Mar 2008
Location: Rhode Island/Florida USA
Posts: 3,372
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Re: Lagoon 450 water pressure pump will not prime when switched over to other tanks
IS there a shutoff on the feed from the tanks themselves? (There should be). With two tanks, if one empties, you need to close the shutoff from the empty tank to the pressure pump. Otherwise, the pump attempts to draw water from the feed line, however the vent in the empty tank and the empty tank itself is what is bleeding air into the feed side of the pressure pump.
Close the shutoff from the empty tank to the pump. The system will pressurize properly.
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10-01-2018, 09:32
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#5
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Registered User
Join Date: Mar 2014
Location: Oz
Posts: 1,042
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Re: Lagoon 450 water pressure pump will not prime when switched over to other tanks
Normal Lagoon 450 valve is a three way, when you open one tank feed it closes the other.
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10-01-2018, 19:52
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#6
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Registered User
Join Date: Aug 2017
Location: Langkawi
Boat: Lagoon 450F
Posts: 4
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Re: Lagoon 450 water pressure pump will not prime when switched over to other tanks
Thank you for responses
I had an airlock in thehose between the hulls,
Pulled the starboard hose off and sucked!
Put some water in the port tanks,got the system primed and it seems to have cleared itself
Thank you for quick responses
Sparky55
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11-01-2018, 10:41
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#7
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Registered User
Join Date: Oct 2006
Location: Cobourg, Ontario, Canada
Boat: Sceptre 41
Posts: 40
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Re: Lagoon 450 water pressure pump will not prime when switched over to other tanks
It's an airlock. Happens on my system frequently when I've rundown the one tank (and refill or switch to second or third tank). My fix was to install a tee fitting at the outlet of the Jabsco pump, a shutoff valve and about 2 ft of water hose (just enough to reach a bucket or the bilge). When it happens, run the pump and use the valve to tap off about a quart of water until you can hear the pump change tone indicating that the air has passed. Shut off the valve and you're ready to go. Got this trick from a helicopter pilot ....
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12-01-2018, 05:26
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#8
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Registered User
Join Date: Oct 2010
Location: Sailing the Mediterranean for 5 years and now sailing in USA
Boat: Lagoon 450
Posts: 53
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Re: Lagoon 450 water pressure pump will not prime when switched over to other tanks
Quote:
Originally Posted by Bean Counter
Switch all taps off. Open faucet on cold in port rear bathroom. Turn on pump. Let it run for about 1 minute - you should get hissing and spitting of water and will then come good.. If still no good, could be clogged strainer or it could be an air leak in the system. We had similar problem and found the in line water strainer at the pump had a crack in the lid.
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I have to second Bean counters answer as 100 per cent right for the solution to the problem ( for us)
-we have had our L450 for just over three years and that procedure has worked every time
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12-01-2025, 07:35
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#9
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Registered User
Join Date: Jan 2025
Posts: 2
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Re: Lagoon 450 water pressure pump will not prime when switched over to other tanks
Hi folks, first off after info on Lagoon 55, if I’m on wrong thread please let me know and direct to correct one if possible. I’ve followed this thread about fresh water supply problem, followed all the tips and still can’t get supply to stop surging. Both starboard and port water tanks are full and showing 100%. Have tried purging air as recommended, switching over both tanks at pressure pump location valves, pump is working. Does same purging from both tanks. Is it possible the bladder in the pressure tank under pump has lost its air pressure, if so any idea of what that pressure in the bladder should be? If I turn pump off at control panel then back on it seems to work fine for a minute or so. Sorry about the long winded question but it’s getting frustrating.
Regards Dan
__________________
Dan
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12-01-2025, 09:43
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#10
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Registered User
Join Date: Mar 2007
Location: Santa Cruz
Boat: SAnta Cruz 27
Posts: 7,198
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Re: Lagoon 450 water pressure pump will not prime when switched over to other tanks
If bean counter's advice doesn't work, then suck the air out of the faucet in the bathroom. It won't take much if the pump works.
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12-01-2025, 14:13
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#11
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Registered User
Join Date: Jan 2020
Location: EC
Boat: Cruising Catamaran
Posts: 1,413
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Re: Lagoon 450 water pressure pump will not prime when switched over to other tanks
The accumulator may have a split bladder. What model accumulator is it? The manual should contain all the detail you need to fix, replace and adjust air pressure.
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13-01-2025, 03:50
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#12
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Senior Cruiser

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 51,775
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Re: Lagoon 450 water pressure pump will not prime when switched over to other tanks
Greetings, and welcome aboard the CF, Dan.
Typically, the accumulator precharge is set to somerhing less than of the minimum system [pump cut-in] pressure.
See “Accumulator Tank pressure” ➥ https://www.cruisersforum.com/forums...re-263319.html
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"
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13-01-2025, 04:00
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#13
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Registered User
Join Date: Jan 2025
Posts: 2
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Re: Lagoon 450 water pressure pump will not prime when switched over to other tanks
Quote:
Originally Posted by Dan1961
Hi folks, first off after info on Lagoon 55, if I’m on wrong thread please let me know and direct to correct one if possible. I’ve followed this thread about fresh water supply problem, followed all the tips and still can’t get supply to stop surging. Both starboard and port water tanks are full and showing 100%. Have tried purging air as recommended, switching over both tanks at pressure pump location valves, pump is working. Does same purging from both tanks. Is it possible the bladder in the pressure tank under pump has lost its air pressure, if so any idea of what that pressure in the bladder should be? If I turn pump off at control panel then back on it seems to work fine for a minute or so. Sorry about the long winded question but it’s getting frustrating.
Regards Dan
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Thank you all, turns out burnt out pressure switch relays on fresh water pump
Dan
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Dan
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