Direct fresh water feed into the boat when at the dock

Jan 4, 2006
7,408
Hunter 310 West Vancouver, B.C.
if you have any empirical data showing that, it might be of interest to others on which to make an informed judgment.
OUCH OUCH and OUCH ! ! !

No empirical data, just advising the OP (and anyone else remotely interested) to err on the side of caution. Don't do it !

As @BCsailor-skier so consicely put it :

Is it really such a pain to fill your tanks, say, 1x week?
Obviously not. And as he further stated :

(A benefit: keeps your tanks fresh and clean.)
Chlorinated water has a way of killing the bugs in the water tank. It's only once the chlorination has disappeared from the water that the tank starts looking more appealing to infectants.

The chance of sinking the boat with a water hook-up is small, the outcome of sinking the boat is catastrophic. Just not worth the risk.
 
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dLj

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Mar 23, 2017
4,728
Belliure 41 Back in the Chesapeake
It’s not so much the inconvenience (which it certainly is to have to constantly refill as in my case it would be more frequent than once a week) as it is the risk of contamination, bacterial growth and critters accumulating in the water we consume, cook with, shower with and wash with when dependent solely on tank stored water. Remember that disinfection, even if dependably effective, doesn’t remove all contaminants.

Everything is a risk. Pick which you prefer.
You must have small water tanks... In my case, i'd never consider putting in a line from the dock. But I carry over 200 gallons of water. If I were living at the dock, and just using water without regard for conservation, I might have to fill up once during the summer. I guess it might depend upon how many folks and shower hogs were onboard... But it certainly would not be much of an inconvenience on my boat.

As far as "critters" in my tanks - I run a high quality filtration system for my fresh water supply. I filter the water as I'm filling and then have a filtration system after my pressure pump. I've never had an issue and have filled my tanks in a lot of places around the world....

dj
 

dLj

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Mar 23, 2017
4,728
Belliure 41 Back in the Chesapeake
OUCH OUCH and OUCH ! ! !

No empirical data, just advising the OP (and anyone else remotely interested) to err on the side of caution. Don't do it !

As @BCsailor-skier so consicely put it :



Obviously not. And as he further stated :



Chlorinated water has a way of killing the bugs in the water tank. It's only once the chlorination has disappeared from the water that the tank starts looking more appealing to infectants.

The chance of sinking the boat with a water hook-up is small, the outcome of sinking the boat is catastrophic. Just not worth the risk.
There's catastrophe waiting at every corner!

dj
 

MFD

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Jun 23, 2016
247
Hunter 41DS Pacific NW USA
My sailboat, and I would expect many others over the last 20 years came with this from the factory.

It is plumbed downstream from the tank water pump, which has a check valve. It has a pressure reducer inline very close to the hose attachment point.

I used it for a few weeks and it was nice but stopped both because I didn’t want to worry about remembering to shutoff the water dockside every time I left, and also wanted to keep the main water tanks in use so they are always nice and fresh.
 
Dec 5, 2017
19
Unspecified Unspecified Where it is
I have dock water plumbed into my lines. Boat connection is in the cockpit, where there is a pressure reducer and an on/off valve
That line connects to the interior host just downstream of the 12V pressure pump. Check valve at the T. Just before that check valve is a T that sends water to the tank selector valve, then to one of the two tanks.

With this system, I can pressurize the potable water system when at the dock and I can use it to fill the tanks (I have deck fills also). It doesn't matter if the 12V pressure is on or off, when the dock water is connected, that pressurizes the system, causing 12V pump to never activate.

Yes, it can sink the boat and one must turn it off; I do whenever I leave the boat. If just quick run to the shore-side head, I turn off at the dock pedestal. When I leave for the night, I turn off the valve at the connection in the cockpit and at the dock pedestal.

Attached is a crude diagram of this part of the plumbing.
 

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Sep 24, 2018
3,879
Catalina 30 MKIII Chicago
I have dock water plumbed into my lines. Boat connection is in the cockpit, where there is a pressure reducer and an on/off valve
That line connects to the interior host just downstream of the 12V pressure pump. Check valve at the T. Just before that check valve is a T that sends water to the tank selector valve, then to one of the two tanks.

With this system, I can pressurize the potable water system when at the dock and I can use it to fill the tanks (I have deck fills also). It doesn't matter if the 12V pressure is on or off, when the dock water is connected, that pressurizes the system, causing 12V pump to never activate.

Yes, it can sink the boat and one must turn it off; I do whenever I leave the boat. If just quick run to the shore-side head, I turn off at the dock pedestal. When I leave for the night, I turn off the valve at the connection in the cockpit and at the dock pedestal.

Attached is a crude diagram of this part of the plumbing.
Does this keep your tanks filled all the time?
 
Dec 5, 2017
19
Unspecified Unspecified Where it is
No, only when I open valve that allows water to flow. I added it to the revised crude diagram. When I want to fill the tanks, I open the valve (red on the diagram), then select which tank to fill. Once that tank is full, I rotate the tank selector valve to fill the other tank. The tank vents spill into shower stall for stbd tank & dive tank locker for port tank, then to bilge. Once water flows out of the vents, that tanks are full. Or I just monitor the gauge.
 

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Sep 25, 2008
7,583
Alden 50 Sarasota, Florida
You must have small water tanks... In my case, i'd never consider putting in a line from the dock. But I carry over 200 gallons of water. If I were living at the dock, and just using water without regard for conservation, I might have to fill up once during the summer. I guess it might depend upon how many folks and shower hogs were onboard... But it certainly would not be much of an inconvenience on my boat.

As far as "critters" in my tanks - I run a high quality filtration system for my fresh water supply. I filter the water as I'm filling and then have a filtration system after my pressure pump. I've never had an issue and have filled my tanks in a lot of places around the world....

dj
I think we have about 200 gallon storage capacity. With 4 aboard, it lasts a few days at most, sometimes less. If it’s the granddaughters, much less:cool:.

Dont know what a “high quality filtration” system is but most are ineffective below 1 micron. Many not even that and completely ineffective on some organics.

I’m familiar with the concern over dock water, however, never read or heard about any real evidence of risk in a well-maintained plumbing system and not a big believer in “what-if” paranoia. We all face and accept far greater risks driving around town.
 

dLj

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Mar 23, 2017
4,728
Belliure 41 Back in the Chesapeake
I think we have about 200 gallon storage capacity. With 4 aboard, it lasts a few days at most, sometimes less. If it’s the granddaughters, much less:cool:.
If one uses 5 days as the "few days", that's 10 gallons per person per day. That's pretty high usage, but I can certainly see how you can go through that much water especially if everyone is showering every day. If I was using that kind of water consumption, I'd go to a direct water feed from the marina in a heart beat...

In my boat I have three showers - but if I'm at the dock, everyone goes to the marina shower - no reason to use the onboard showers. But that's just my usage, as I originally stated....

Dont know what a “high quality filtration” system is but most are ineffective below 1 micron. Many not even that and completely ineffective on some organics.
Feeling kind of Déjà vu here...


I’m familiar with the concern over dock water, however, never read or heard about any real evidence of risk in a well-maintained plumbing system and not a big believer in “what-if” paranoia. We all face and accept far greater risks driving around town.
I can't agree with you more on this one!

Just a couple observations: Anyone with a well water - how many of those users do you think actually test their well water? Anyone with municipal water - how many actually check that water coming into their homes? The answer to that is the vast majority in both cases do not.

But we get really paranoid about water on our boats... Driving around town? I'm not even going to go there.... hahahahaha

dj
 
Sep 25, 2008
7,583
Alden 50 Sarasota, Florida
Just a couple observations: Anyone with a well water - how many of those users do you think actually test their well water? Anyone with municipal water - how many actually check that water coming into their homes? The answer to that is the vast majority in both cases do not.



dj
There is lots of inconsistency between what people say and what we do:

Never test home potable water but obsess over boat water quality.

Lament the heat generated by colored topsides but drive to/from the boat in a black car.

Depend on the marketing language used on water filter packaging.

Search endlessly for the cheapest insurance but never checking on the underwriter’s residual capacity to pay out or if there is actually any nexus between the misleading umbrella name they use to hide their independent financial capacity.

Religiously avoid dock water connection but have no clue where or what condition thruhulls and the hoses are.

And my favorite monumental oversight - not having an ice maker aboard:yikes:
 
Jan 7, 2014
453
Beneteau 45F5 51551 Port Jefferson
I'd wire a solenoid valve into the system. Turn it off when leaving the boat. My boat already has a water alarm when the second bilge float gets tripped.I I generally shut the water pump off when I leave my boat. I have had the hot water t/p valve open or a tank that was borderline empty trigger the pump while away from the boat and come back to a pump running til it overheats. Don't power boats use city water?
 
Jun 2, 2004
3,598
Hunter 23.5 Fort Walton Yacht Club, Florida
There is lots of inconsistency between what people say and what we do:

Never test home potable water but obsess over boat water quality.

Lament the heat generated by colored topsides but drive to/from the boat in a black car.

Depend on the marketing language used on water filter packaging.

Search endlessly for the cheapest insurance but never checking on the underwriter’s residual capacity to pay out or if there is actually any nexus between the misleading umbrella name they use to hide their independent financial capacity.

Religiously avoid dock water connection but have no clue where or what condition thruhulls and the hoses are.

And my favorite monumental oversight - not having an ice maker aboard:yikes:

I am always amazed and almost physically disgusted when I see folks using the hose at the pumpout to fill their water tank. Did they not see what and where the guy at the pumpout before them was doing with that hose?
 

capta

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Jun 4, 2009
5,001
Pearson 530 Admiralty Bay, Bequia SVG
Certainly one of the quickest and most common ways to sink a boat at the dock. "Danger Will Robinson, danger!"
 
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Nov 20, 2025
20
Alden 60' Schooner Killybegs
This isn't something I would consider doing but I don't spend much time at docks, as a rule anyway. But, if this is something you really want, ignore the naysayers. It can be done. You just need to do it right and know the risks.

At some of the touristy ports in Europe and Asia, I sometimes see this on big powerboats. I assume the systems were designed from the beginning to work this way and not retrofitted. I have only known one person who did this as a retrofit on their sailboat. They had a simple solenoid that failed in the closed position. So, if they lost power, it closed. But more importantly, a float trigger in their bilge also closed the solenoid. They loved it but complained that the float was too low and that taking a shower could sometimes cut the water as the shower drained into the bilge.