How does this water tank setup work (or does it not)?

[chris-s]

I've been looking at the water tank setup on our 'new-to-us' boat which has had a second water tank added in the v-berth trying to work out how it can work as it is plumbed. I think the plan was that the water from the new tank gets drawn into the original tank by a vacuum effect from running the pump, but the orignal tank is still vented so that can't happen (and there are no one-way-valves anywhere). But even if it wasn't vented, I believe it still wouldn't work as eventually it would effectively be vented via the shared fill pipe to the new tank and then thru the new tanks vent pipe. Currently the original tank is 90% full and the additional tank just an inch or so. Of course the easy option might sound like just fill both tanks and see what happens, but there is no access to running water where it is ashore.

Chris

 

[ChromeDome]

If you move the blue line to go from bottom to bottom on both, it will work.
You then don't need the fill to go to both as water will go in both directions.
The vent can go between the tank tops

 

[ChromeDome]

Double post

 

[chris-s]

If you move the blue line to go from bottom to bottom on both, it will work.
You then don't need the fill to go to both as water will go in both directions.
The vent can go between the tank tops

It would work...only the original tank is tapered and access restrictions etc so I couldn't do it in quite that manner, but I had thought of taking the 'bottom green vent line' from the additional tank and running that back to the pump inlet to achieve the same thing.

 

[Pete7]

Chris, are they on the same side of the boat or one port and the other starboard? If so and it's a yacht when you tack that's a lot of water going to change sides to leeward just what you don't want.

 

[chris-s]

Chris, are they on the same side of the boat or one port and the other starboard? If so and it's a yacht when you tack that's a lot of water going to change sides to leeward just what you don't want.

Original tank to starboard (150litre ?), additional 80 litre tank centred in the v-berth. I can't imagine we really need both, given we managed with a 40litre tank in our previous boat, so might just disconnect it completely, but I'm really puzzled as to how it could ever have worked - if it ever did!

Chris

 

[Plum]

Original tank to starboard (150litre ?), additional 80 litre tank centred in the v-berth. I can't imagine we really need both, given we managed with a 40litre tank in our previous boat, so might just disconnect it completely, but I'm really puzzled as to how it could ever have worked - if it ever did!

Chris

I don't see how that would ever work as it is. Unless you need the extra space I would leave it there, move the lower blue hose so it Tees into the pump input, put two ball valves in the blue hoses just before the Tee so you can select either tank or switch both off for pump maintenance, put a switchover valve in the fill hose and put a valve in the vent of the bow tank. This will mean you only use the original tank but have the option in the future to increase capacity, keeping the two tanks independent in case of contamination. While you're at it you may want to consider a winter draindown valve in the lowest part.

These valves work well Hose Tail Plastic Ball Valve AIRPRO

Www.solocoastalsailing.co.uk

 

[cpedw]

Are you sure the heights of tanks are as you have drawn? Or perhaps when you're moving fast, the trim change moves the additional tank up enough to transfer water to the original tank.

 

[Pete7]

Original tank to starboard (150litre ?), additional 80 litre tank centred in the v-berth. I can't imagine we really need both, given we managed with a 40litre tank in our previous boat, so might just disconnect it completely, but I'm really puzzled as to how it could ever have worked - if it ever did!

Chris

Can't see you needing that much if coastal sailing. Disconnect, clean with weak bleach and dry. Check occasionally to see if water has flowed via the vents from the original tank to the fwd tank if over filling. That's 80kgs saved from the bows which is good unless you really need it.

 

[penfold]

Not exactly a burden to tee the pump suction and have suction to either tank via separate valves(or a multiway if preferred); daft attempt to have it work automatically, it's preferable to me to have it switchable anyway.

 

[ChromeDome]

The principle of communicating vessels would make this work