Two tanks one pump out deck fitting

[Panta Rei]

Is there any regulation or practical reason two tanks can not be connected to a common deck pump out?

 

[Squidd]

I'm guessing they won't pump evenly and when one sucks air the other will not pump out leaving you a quantity of "material" still in one or both tanks...

 

[woodster]

Is there any regulation or practical reason two tanks can not be connected to a common deck pump out?

dont know about the regulation part.... but i dont see why if you installed "wye" valve to both exit hoses it couldnt be done but it does mean you would have to pump one and then change the valve over and pump the other one....

regards

woody

 

[Peggie Hall HeadMistress]

There's no regulation that prohibits connecting two tanks to the same pumpout fitting, but it never works very well unless there's a y-valve in the pumpout line that allows each tank to be pumped out separately. Another y-valve that also allows the tank to be dumped would create a plumbing nightmare, but that doesn't seem to be likely in your case.

How far apart are the tanks? Iow, will the two pumpout lines be about the same length, or is one a lot longer than the other? 'Cuz that can have a lot do with how well it'll work.

 

[Bill Roosa]

You could put separate vent lines on each tank then control them with two well placed ball valves to prevent one tank from "sucking air" Course that tank will see full pump-out vacuum so this may be what you call a "stupid solution"

 

[Panta Rei]

Thanks!!

Thanks for all the help.

I'll add a bit more information.

I will install a 15 gallon tank under the forward v-birth and a 20 gallon tank under the starboard settee. I have no delusion of these being aerobic.
The old forward deck pump-out on the starboard side (about even with the mast ) must be eliminated.(another story)
The deck pump-out servicing the settee tank is on the starboard side even with the companion way
I'm guessing that it will be a 20 ft. run from the forward tank to the deck pump-out. I can do most of the horizontal run (about 12 ft) in PVC pipe.
The forward tank will be higher than the settee tank.
I have room for shut offs at each tank or a y under the deck pumpout.
The hose runs look reasonable with no big dips or loops.
I'm not opposed to doing something creative (that must be redone if unsuccessful).

 

[Peggie Hall HeadMistress]

You could put separate vent lines on each tank then control them with two well placed ball valves to prevent one tank from "sucking air" Course that tank will see full pump-out vacuum so this may be what you call a "stupid solution"

Yup...that IS what I'd call it! 'Cuz it would just about guarantee a cracked tank, if not two of 'em before this year is out. Both tanks MUST be vented separately....whether they share a single deck pumpout fitting has nothing to do with it.

Whether the two tanks are connected to a single deck pumpout shouldn't have anything to do with keeping the tanks aerobic, either. The tank going under the v-berth should be vented off the top at the bow end of the tank and the vent line run forward. Spend a little time in the Head Mistress forum researching the reason for this.

The deck pump-out servicing the settee tank is on the starboard side even with the companion way I'm guessing that it will be a 20 ft. run from the forward tank to the deck pump-out.

That's way too long for any line in any sanitation system, hard pipe OR hose. You'll have nothing but problems with it. You're gonna have a tank in the bow and a tank midship...You'll be a lot happier with the results if you install a new deck pumpout fitting midway between the two tanks instead of moving tank contents almost a whole boat length.

If you'd like to brainstorm how to do it right, send me an email...I'll be glad to help you.