Position of inlet

[David W]

Hi Peggy, firstly want to thank you for your contributions to this forum. I have learned a great deal from the posts and all the responses.On to the question...Does the position of the tank inlet on the tank dictake how much of the tank volume is usable?Hypothetical situation: Square tank, capacity 5 gal. If the inlet is positioned halfway up the side of the tank, is the usable volume of the tank 2.5 gals?My situation is this. I have a rectangular tank that I have to mount on an angle.The low end is nearest the head & the output through hull (note Canadian sailor). I was initially going to put both the inlet & outlet on the top of the tank at the low end.Now I am thinking that it would be best to put the inlet and the two 1" vents at the high end and put the outlet at the low end.Comments? Advice?ThanksDavid

 

[Peggie Hall HeadMistress]

Yep...if you put the inlet halfway

up the side of the tank, the useable capacity of the tank will drop to the level of the TOP of the inlet fitting. Any more will run back into the head discharge hose and end up trying to get back into the toilet bowl. But there are also other issues...a 5 gallon tank--even if you can use it all-- doesn't hold enough flushes to be worth the effort to install it. The average flush is .6 gallons...the d'd thing will only hold about 9 flushes, which is less than 2 people are likely to put into in one day.I think we need to get together via email (I'm in all the directories) to spec out a system you can actually use.

 

[David W]

Sorry Peggie, I should have been more clear

5 gallon tank was only for illustration purposes. I am planning on using an 18 Imperial gallon tank.

 

[Peggie Hall HeadMistress]

That's a reasonable size...

Your original idea of putting both the inlet & outlet on the top of the tank at the low end is the best plan. Because waste falls into the tank, it doesn't matter whether it's at the high end or the low end...the tank will fill up just as fast no matter where on the top it comes in. Just be sure to put the inlet and vent fittings INBOARD--toward the centerline of the boat--to prevent tank contents from spilling into the vent line and head discharge hose when you're heeled.Btw, what tank mfr is supplying the tank?

 

[David W]

Wait a sec...

just to clarify. In my question I stated:"My situation is this. I have a rectangular tank that I have to mount on an angle.The low end is nearest the head & the output through hull (note Canadian sailor). I was initially going to put both the inlet & outlet on the top of the tank at the low end.Now I am thinking that it would be best to put the inlet and the two 1" vents at the high end and put the outlet at the low end."You replied and said:"if you put the inlet halfway up the side of the tank, the useable capacity of the tank will drop to the level of the TOP of the inlet fitting. Any more will run back into the head discharge hose and end up trying to get back into the toilet bowl."If I put both the inlet and the outlet at the lowest end of the tank, then the usable capacity would be reduced because as soon as the tank level is even with the inlet I can't put anymore into the tank.So my plan is this:Low end of the tank = top centre mounted outlet with standpipeHigh end of the tank = top centre mounted inlet and 2 vents.The tank is from Century Plastics in Vancouver BC. 3/8" wall