How To Not Sink Your Boat

Project date: 2006



If you have a cruiser type boat, its likely that you have all the comforts of home, including a fresh water system.  For many boats, the source of water for the system can come from either a fresh water tank with an on-board pump, or via a “city-water” inlet.


The city-water inlet consists of a common garden hose type inlet that provides a constant supply of fresh water. This of course, is only available when you are at the dock. 




The conventional dock wisdom around many marinas is that you should only use the city-water inlet when you are present at the boat, since any malfunction of the system may allow an endless supply of water to enter the boat.  The bilge pumps may keep up with the water flow for a time, but eventually the pump or batteries may fail, which at that time, your boat will sink.


For this reason, regardless of the actual risk, some boaters will not use the city-water inlet system at all, but rather rely solely on the on-board water tanks for their water supply.


Sinking example: This boat actually sunk because on a windy day, chafing of the water hose caused it to burst inside of the boat.



Some boats have their city-water inlet located inside of the boat, behind a hatch.  This typically involves the water hose being routed through an opening at the hatch.  If the hose is not routed correctly, chafing can occur and allow the hose to burst – which is what happened in this situation.




Another source of sinking with the use of city-water is that any fitting on board, should it fail, will let water into the boat.  As many areas of the modern cruiser are not easily accessible, and as the boat gets older, a water leak could occur without the boater’s knowledge. 


In the photo above, this is a factory plumbing job in an older, popular brand boat. Do you think this will ever become a problem?  Should this ever become a source of leaking, it might go undetected until it’s too late.


To prevent sinking, two techniques should be used.


  1. Be sure to turn off the water when you leave the boat unattended.
  2. Use a timed water flow interrupter.


The water flow interrupter I am using is called “The Flow Guardian”.  Essentially it is a metering system that allows the water to flow for a limited amount of time.   It is very simple to use; just connect it to the hose between the dockside water spigot and the boat’s city-water inlet, then dial-in the number of hours to allow the water to run.  The metering system itself is powered by the water flow, so there is no requirement for electrical power. Think of it as a mechanically timed valve.



When we arrive at the boat, we have found that setting the Flow Guardian for about 3 hours will provide sufficient water for the weekend. 


While it is prudent to turn dockside water off prior to leaving the boat for any length of time, it is something easily forgot. In that event, using a device such as the Flow Guardian provides an extra measure of safety, and the best practice would be to do both. 

In the event of a major leak while the boat is unattended, the Flow Guardian will shut off the water after the prescribed 3 hours (minus the amount of water we have used over the weekend).  The 3 hour window will hopefully allow the bilge pumps to keep up so that the boat does not sink.  Of course, you can set the window to any amount of time  you wish. 




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