Dual water tank check valve?

[jonelli]

Okay, moving onto a much cleaner fluid topic, I was prepping the boat for a long trip today and decided to bleach out my water tanks. I have two, the normal one under the starboard settee and the forward one under the V berth. The V berth tank has its own shutoff valve - ok. The hose from the forward tank goes past the starboard tank to a T where there's a non-working check valve coming from the starboard tank before the T.
I can't pump the last third of the forward tank unless I disconnect the T and plug it with my finger sonthe pump can get it all out of the forward tank.
I can't figure out what the check valve if it were working would actually do, and I can't think of an elegant solution for getting all the forward tank water out without some kind of manual shutoff valve at the T to plug up the starboard tank.

Any ideas? If I can't figure anything out easy and quick I guess I'll resort to a manual shutoff valve for now so at least I have "easy" access to that water on my trip.
Sent from my iPhone

 

[JamesG161]

non-working check valve

Murphy's 3rd law...

Check valves Don't!

Without knowing the relative elevations of the V-berth tank to the settee tank, I suspect the V is higher and the check valve was an attempt to use the V first the finally the Settee last. The Settee one might overflow, if V is too high level.

In short term, fill V and shut off manually. Fill Settee and use it first. When empty, open V valve. Even if the Check valve leaks to Settee, who cares.
Jim...

 

[jonelli]

Hey Jim,
All of that is correct and already how it is setup with one flaw.
When the settee tank is empty, it sucks air and will not draw that last 1/3rd from the forward tank.
thats the real problem. So even if I shut off the forward tank, once the settee tank is empty, it will only draw the water from the V that is higher then sucks air.
I have to block the settee tank from sucking air somehow.

 

[jonelli]

I should also add that the line that comes from the forward tank goes over the top of the settee tank to the pump.
The settee tank line comes from the bottom and goes up to the above line in a T.
I'll draw a picture.

 

[SG]

Jonelli:

I suggest putting in a diverter valve - (Y Valve, whatever you call it). Then just chose which tank.

I'd clearly draw down the bow tank on your Catalina 30 first, then I'd go to the more centrally located tank.

There's trim and sailing differences if you un naturally load the front of your boat. It should perform better with the load being more central and lower.

http://www.thebosworthco.com/bselectv.php

 

[JamesG161]

Sounds like a piping routing problem or you water pump suction placement.

If the bottom of the V is higher than the Settee, it should gravity drain to S.

Are you sure of V tank level?
Jim...

 

[JamesG161]

I should also add that the line that comes from the forward tank goes over the top of the settee tank to the pump.

Just saw this...
That is the Routing Problem!
Jim...

 

[jonelli]

This is basically it

 

[JamesG161]

If elevations shown in your drawing are relative elevations to each other, then this must be happening...

1) V berth tank is empty or...
2) Water line from V to Pump has a low spot or dip below the check valve top elevation at some piping point.

A leaking check valve would fill the S tank when not pumping.

____
Air will flow easier than water to the pump suction.
Jim...

PS: I don't think at this point of info, you have a check valve issue.

 

[jonelli]

My picture isn't perfect, so yes, I would say that the originating line from the V tank is BELOW the check valve at the T.
But, the check valve is not working anyway. I think the check valve would only keep the V from filling the S back up.
But, in my case, it's good that it's not working because some of the water I can't suck out might go into the S and get sucked out.

Okay, so correct me if I'm wrong, but it sound like those lines all need to be BELOW the water tanks, and then they'll both drain etc... right? For now, I'm going to go buy a little manual valve so I can suck out the left over V water if I need to.
I'll have to revisit this later.

 

[JamesG161]

all need to be BELOW the water tanks,

Pump suction too, but not always practical.
Jim...

 

[kloudie1]

One way to fix it (temporarily) would be to put block valve in the settee tank vent line.. When you want to use the forward tank, shut the settee vent off and the pump will pull down the forward tank first, since it is at a higher elevation. .. do make sure you have a good clear working vent on the forward tank before you try that..

 

[jonelli]

I just installed a gate valve where that check valve is. I'll leave it open as my "reserve" in an emergency if I need that extra water I'll just close it.
I'm going on a 9 day trip of the Channel Islands on Saturday.

 

[JamesG161]

put block valve in the settee tank vent line.

Very clever idea!
Jim...

 

[jonelli]

So, long term, somehow I just need to route the lines below both tanks, right? Then it should draw from both no matter what, right?

 

[SG]

I don't think so. Make sure each tank has a vent (that can't be compromised by seawater). Have a discrete valve that only draws water from one tank at a time. Then, as long as you're "pick-up" from the tank is low, you'll be positively sucking water.