Check valves between water tanks

[HeartWarrior]

I'm in the process of replacing the fresh water lines between my forward and aft tanks and found that there is no check valves between the two tanks. I ask this question since it appears that when I fill up either of the tanks the water will flow to the other tank and appear to fill both tanks at the same time. I would like to keep the filling process separate and was going to install check valves on the output side of each tank so this does not happen.

Just looking to see if anyone has done this and found it to be problematic for any reason. I cant find any reason why it would.

Thanks for the help.

 

[DavidM]

Unlike raw water cooling systems where check valves are sometimes considered, I don't think you need to worry too much about check valves sticking in potable water service.

I assume the fresh water pump will draw from both tanks through the check valves. FWIW that is very likely to cause one tank to be drawn significantly lower than the other one. Small differences in hose runs and turns on the suction side of a pump will make big differences in water flow between them. I would want a block valve in addition to the check valve to force water to be drawn from the fuller tank if this happens.

I guess if you rigorously manage filling and using water from your tanks it will work ok. Most people just want the tanks to equalize during use so they don't have to worry about them.

David

 

[jgwinks]

I'm new to trawlers, but on the sailboats we don't normally connect multiple water tanks together at all. You use valves to select which tank to draw from, but never more than one at a time. On the last boat one tank was much smaller than the other. We would draw from the large one and when it ran dry we switched to the smaller one as a backup, and start looking for a refill opportunity.

 

[smitty477]

"Just looking to see if anyone has done this and found it to be problematic for any reason. I cant find any reason why it would."

We always found that shut off valves between our two water tanks to be very helpfull in a number of ways...
- we always could reserve one tank and knew exactly how much was left
- filling each tank fully was possible with the valves
- drawing from each tank fully was possible with the valves
- if one tank were to leak, or a water line left open, or a tank got contaminents in it the other was preserved.
YMMV

 

[OldDan1943]

Just put in an isolation valve between the 2 tanks.
My N46 had about 5 isolation valves for the 5 tanks.
I think they used the FW as ballast and buried them in the keel.
First cruise, I did not top off the water tanks and ran out of water. I did not discover the 5th isolation valve till the end of the cruise. After that, I topped off all the tanks isolated all but 2 tanks, fwd port and starboard tanks. Never had trouble again. The 5th tank was the smallest tank.
I did install a 150gpd water maker...... The intent was, if I started to get low, turn it on and over 5 or 6 days, fill the water tanks. Never used it.

 

[jgwinks]

Considering the different environments of power vs. sail, I can see an advantage in having the tanks connected together on a powerboat if they are positioned port and starboard. Drawing one tank down before the other would affect the boat's trim. This would be a good argument for not having check valves, or having manual valves that are normally left open. On a sailboat this is exactly what you don't want to do, as the boat heels water would flow from the high tank to the low one and make the boat heel more. Some sailboats even have ballast tanks or use the potable water tanks to pump water to the high side and flatten the boat out. If the tanks are arranged fore and aft it wouldn't matter as much, and the advantages of keeping a reserve, isolating contamination, etc might take precedence.