Fresh water filling when hooked to shore water feed

B

Brent Nutting

Well-Known Member
Mar 24, 2016
664
Lk Saint Clair, Fair Haven, MI
Boat Info
2002 480 Sedan Bridge
10' Aventus RIB w/ 9.9 Merc
Engines
Cat 3196
Hi everyone, I first posted the below in the 480DB Owners portion, but thought it would be better posted here.

Hey guys, I am hoping to once again pull on the great knowledge base of this club. This past weekend, while on a quick 4 day trip, I noticed that when I am hooked to the shore water line, I am filling my fresh water tank too. I noticed a slight drip from the overflow area and checked the tank level. I had 3/4 and once hooked to the land water feed, the level increased to full. I am not sure if this has happened to anyone before, just looking for any feedback from someone that might save me a lot of time just investigating.
Thanks in advance.
 
Don't know how your boat is plumbed but on my boat that could only happen if it was able to backflow through the fresh water pumps.
 
We only have a little 240DA. But, my shore water is not connected at all to my fresh water tank.
 
my3sons said:
Don't know how your boat is plumbed but on my boat that could only happen if it was able to backflow through the fresh water pumps.
Click to expand...
I think that's what's happening. One of the fresh water pumps is kaput.
 
Thanks guys. From some general reading, I thought it might be related to the fresh water pumps. The fact that I keep hearing the pump cycle when on is also leaning towards the pump being the issue.
 
I’ve been told never to leave my boat with the shore water connected and on. If there is a break/leak, the shore water can overcome the bilge pumps and sink the boat. I’m guessing this is okay for now, since it appears the freshwater tank fills, and the overflow is going outside the boat. But if something changes, your boat could sink.
 
Todd320 said:
I’ve been told never to leave my boat with the shore water connected and on. If there is a break/leak, the shore water can overcome the bilge pumps and sink the boat. I’m guessing this is okay for now, since it appears the freshwater tank fills, and the overflow is going outside the boat. But if something changes, your boat could sink.
Click to expand...
Hey Todd320, sorry my original post may have been a bit unclear. I never leave the boat hooked to the shore water unless I am on the boat. The issue is while I am hooked to the shore water feed (am I am on the boat), the shore water feed is still filling my fresh water tank, even though I am hooked to the shore water feed. I think the issue is related to the fresh water pumps, as some other members have stated might be the issue.
 
I am surprised there isn't a check valve on the shore water side of the pump to prevent this
 
Soulshine said:
There should be if this is a factory installation.
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I looked at my parts list and the only check valve is on the water heater.... Which makes me think the fresh water pump acts like a check valve if it's working right... But still why back flush the filter back into the tank if the pump is malfunctioning
 
I installed a shore water inlet in my boat last season. I couldn’t believe it wasn’t equipped with one from the factory.

After reading many how to articles and posts here and there I understand that the check valve protects the pump.

If the shore water is on, there would be pressure into the outflow of the pump. No problem unless the pump is turned on in which case the pump would likely be damaged.

I installed a bronze one way valve and T fitting that sends the shore water right into the manifold. When away from the dock, the pump’s pressure opens the valve and water from the tank goes to the manifold.
 
Your freshwater pump should have a check valve built into it. This is what keeps the pressure in your lines when your running your freshwater pump. It's also what keeps the dock water from back filling into your freshwater tank. Given your comment about the freshwater pump kicking on frequently, and your backflow issue -- sounds like the checkvalve is leaking a bit.. either its worn, or there is something in there.

Assuming you have a Shurflo (most common fresh water pump), its section 3 on the diagram. Take the whole thing apart, clean it and see if it survives (or replace the parts). Note: Typically all water needs to be off, including dock water - in order to remove the freshwater pump (depends on if you have valves inline). You may also need to turn your hot water tank off as well - if there's no water pressure/flow available.
http://riverbendind.com/content/MiscPDF/Shurflo-2088-Series-Parts.pdf

As a side note, there is also a check valve at the dock water connector itself - either integral or right behind it. This check valve keeps your freshwater pump from pumping water out the inlet.

Good luck!
 
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