3807 Fresh Water Tank Loosing Water

[Raylap819]

I keep filling my fresh water tank every week even though I use very little fresh water. Obviously there’s a leak somewhere. The pump was recently replaced by the former owner and it does look new from what I can see. When I use water, there is always air in the system and it spits out the faucet. I’ve looked inside the tank with a camera and the tank appears to be sound. Does anyone have the fresh water system diagram for a 3807 or the likes. Are there valves to shut off the aft and forward heads (sink and showers)? Did anyone experience this? Also, seems difficult to access the pump to tighten all hoses/fittings. Any suggestions. Appreciated, Ray

[g36]

Does the pump cycle on occasionally by itself if you use no water at a faucet etc. ? If it does then leak is on the pressure side of the pump after the pump but If not leak would be before the pump. The previous owner may not have gotten clamps tight on hoses when replacing pump. Do you find any water in the bilge? There's not going to be cutoffs at the sinks etc like a house. Do you have a outside shower or washdown those are places to also check for leaks.

[km1125]

On the "there is always air in the system" part... Check to see if there's a screen between the tank and pump. There is usually one there to protect the pump from debris. If it gets clogged then any minor leak between there and the pump will allow the pump to suck in air. Actually, whether you have a screen (which is recommended btw) or not a leak between the tank and pump will cause both the tank to lose water and the possibility of sucking air into the system, so you might want to thoroughly check that part of the system out.

[Viper]

I agree with all the above. If the pump is in the original location under the step, it's a real pain to get to and is why I'm getting ready to relocate mine as I want to upgrade it anyway. For that vintage, you also likely have a Qest plumbing system (grey lines and fittings) which is known to spring leaks periodically at the fittings as they get older, this can be due to improper winterizing as well. There are no shut-offs from factory in the system unless a previous owner installed them.

Lots of possibilities for sources of leaks, anywhere from the tanks, lines, fittings, faucets, strainer, pump, ice maker, bar faucet, etc. Don't forget the hot water heater, for that vintage, its tank may already be leaking. Air in the system is usually an indication that something is loose or cracked before/at the pump. As mentioned, if the pump cycles periodically without running a faucet, you likely have a leak after the pump or the pump's check valve is leaking and it's draining back to the tank.

If you fill the tanks at the end of the weekend, turn the water pressure off, and return Friday to find they're empty and there's water in the bilge, chances are pretty good you have a leaking tank/s or lines, fittings, or strainer leading to the pump. If the tanks are still full when you return, you have a leak on the pressure. For that, turn your pump on or dockside water and then it's a matter of checking all areas bow to stern where there may be plumbing hardware, especially fittings and fixtures.

Good luck and let us know what you find.

[buster53]

I’ll pass this on for what it’s worth….
Some years ago, I had a 3807 and my water pump went bad and needed to be replaced. I spent hours looking at that pump, running it over and over in my mind as to how to replace it. I was stumped. Then one day the light bulb turned on..
Don’t take the pump off the mount frame (basically impossible). Remove the mount frame from the boat with the pump attached to it. After it’s out, replace the pump and remount the frame back to the boat. Once I figured that out, it wasn’t that difficult a job to replace the pump.

Replacing the pump in a 3807 was way easier than my 356. That was a PITA.

[Viper]

Better yet, do what I'm doing and relocate the pump to the other side of the bulkhead so it's in the engine compartment, way easier to service then, especially since the OP is in a need to winterize climate.

[Raylap819]

Thank you all for your suggestions. The pump comes on after 5 minutes or so if the breaker is left on. It stops for a few minutes and comes back on again. I don’t hear any water running nor do I see any wet spots. Baffles me! There appears to be two tanks, one that I can see at the top of the hallway leading to the forward bedroom and the other, larger, in the hallway in front of the galley. The pump is under the stars leading o the hallway and is very hard to access. Today I found a ball valve installed on the pipe leading out of the pump. I’ve tighned every fitting I could find but could not do any test since I’m out of water. The Marina where I am does not have clean water so this week I’ll go fill up and check to see if anything is solved. Also will run the pump with the valve shut so that will eliminate any leakage after the pump. Again thank you so much for your help. Ray

[Raylap819]

Also, how can I check if there is a screen between the tank and the pump. I can hardly get to the output side of the pump. Any suggestions? Thanks Ray

[Raylap819]

Also found a round canister with the words « Water Puppy ». It’s attached to the output side of the pump. Might be a priming thing???

[buster53]

First of all, replacing the pump isn’t as bad as it looks, but it sounds like the pump is fine as it is pumping water as needed.
The leak could be anywhere. Last time I had a leak in my system, I found it right near my water heater and it was a pinpoint leak, not easy to see.
The 3807 has 2 showers, one water heater and 3 lavortories…meaning, there’s a lot of water piping in the bilge and hidden in walls and behind bulkheads. Tracking down a pinpoint leak will not be easy.