Proper Head Tank Installation ?

[Ocean Roads]

When installing a new head tank set up in a boat, does the discharge suction end of the hose go at the bottom or the top of the tank?

One "expert" has told me it goes on the top of the tank, and the suction of the pump out station will suck it clean.

Another person told me it must go at the bottom end of the tank to be able to be sucked out.

[Pete7]

Originally Posted by Ocean Roads

One "expert" has told me it goes on the top of the tank, and the suction of the pump out station will suck it clean..

Like you, I can't see how that is going to work, especially if there is a separate air vent to the tank which is almost essential.

UK website, but might something useful here:

Holding Tank Plumbing and Layouts | Tek Tanks

Pete

[motion30]

bottom

[HopCar]

Normally rigid tank bottom, bladder tank top. Does your tank happen to have a pickup tube that runs from the top of the tank to the bottom? Only then would you put the discharge hose on the top of a rigid tank.

[Ocean Roads]

I am building a custom tank set up in my boat.

Any good websites for semi custom AFFORDABLE holding tanks?

[DeepFrz]

If you look down at the bottom of this page you will see links to other threads that discuss this issue. Some of them have links to tank manufacturers.

[Unicorn Dreams]

My tank has 4 fittings.

On top 1 vent line, 1 intake, 1 pump out port.

On the bottom it has 1 drain for over board discharge..

[peghall]

All tanks--water, fuel, waste, have to be emptied from the bottom. However that doesn't mean that the discharge FITTING has to be at or on the bottom of the tank...it can be on the top of the tank, with a pickup tube inside the tank that goes to the bottom. It's my preferred way to do it because it eliminates standing waste in the discharge line. However, installing all fittings in the top of the tank does require at least 5" clearance above the tank.

If the tank is to be set up to dump at sea, I also prefer TWO discharge ports in the tank--one with a line that goes directly to the deck pumpout fitting, the other directly to the overboard discharge pump. This eliminates a y-valve.

Inlet and vent fittings should be installed away from the hull, toward the centerlne of the boat, to prevent tank contents from spilling out the vent or running back toward the toilet when the boat is heeled.

Ronco Plastics (no relation to Ron Popeil and his pocket-vego-fishing-pole Ronco) Ronco Plastics is your best source for a tank. They make TOP quality rotomolded water and waste tanks for a very reasonable price and have more than 400 shapes/sizes, over 100 of which are non-rectangular...and they install fittings in the sizes and locations specified by the customer when they make the tank.

I'll be glad to help you spec the whole thing out if you'd like to send me an email.

[Carl-T705]

Maybe this schematic may help. From James Baldwin's ATOM website.. I also had one for a tank mounted above the waterline where discharge at sea is simply opening a valve and no pumping or Y valve, everything always goes into the tank. let me look for it. Carl

[Carl-T705]

Here it is , from Southwinds article, Hope you can view it.. Carl

[chrisferro]

Listen to Peg, she knows her stuff!

If your Discharge fitting has a tube (also known as a "standpipe") that is cut at a slight angle at the very bottom of the tank, it will suck the contents out through the top. The only downside is that you can never get the very last bit of waste out, but the upside is that you have no waste sitting in your hoses which will eventually get permeated and stink the boat up. In Carl-T705's diagram above, you'll see that waste will settle and sit in that discharge hose that is connected to the "through deck outlet". You don't want that (sorry, Carl). It also means that you can disconnect your hoses to replace them, and not have to worry about poop spilling out all over the place (been there, done that!)

Good luck,
Chris Ferro
Electrosense

[swisscraft]

Hi, I have a bottom valve - indeed a very bad thing! If it leaks its a nightmare if you have standing waste in you hose (and you will) its not better. But my tank is below the bottom - if you have space put the tank up!

I prefer a gravity holding tank higher in the boat - hose from the toilet goes in to the top and discharge on the bottom by gravity - and thats the only time I would install a valve on the bottom. Even if it means waste go always trough the tank there are several advantages:
- Most of the time you do not need any vent in the hose from the toilet to the tank as the tank is vented (less trouble and less smell)
- You avoid any Macerator Pump & easy to discharge
- You can install a big short vent line = less smell
Just do not forget to ensure you have two vales on the discharge line: One right below the tank and then the trough hull - you avoid any standing waste in the discharge hose...

[delmarrey]

Originally Posted by chrisferro

Listen to Peg, she knows her stuff!

If your Discharge fitting has a tube (also known as a "standpipe") that is cut at a slight angle at the very bottom of the tank, it will suck the contents out through the top. The only downside is that you can never get the very last bit of waste out, but the upside is that you have no waste sitting in your hoses which will eventually get permeated and stink the boat up. In Carl-T705's diagram above, you'll see that waste will settle and sit in that discharge hose that is connected to the "through deck outlet". You don't want that (sorry, Carl). It also means that you can disconnect your hoses to replace them, and not have to worry about poop spilling out all over the place (been there, done that!)

Good luck,
Chris Ferro
Electrosense

I'm with you on this and a lot of the tank builders are now recommending a stand pipe (pick-up tube) as well.
My old tank is right in the solon under a set and the outlet fittings has always seeped just enough to create an oder so I only have used the tank when it absolutely required. Not good!

I have a new tank ready to go in when I do some forward modifications. I had it built with top fittings only, with the pick-up tube tucked in the aft/lower corner and a 3" access cover for flushing (it's longer then the drawing shows). I will no longer have to worry about a leak. It'll tuck in just forward of the head along the curve of the hull.


.

[peghall]

- Most of the time you do not need any vent in the hose from the toilet to the tank as the tank is vented (less trouble and less smell)
- You avoid any Macerator Pump & easy to discharge
- You can install a big short vent line = less smell

Two out of three ain't bad. No need for a macerator pump is only one that's unique to a gravity drain tank...the other two would be true no matter how the tank is emptied.

You're right that there's no need for a VENTED loop in the toilet-tank line in ANY installation...However, if the inlet fitting on the tank is in the wrong place (which it is in most installations), an UNvented loop can be a good idea to prevent waste that spills into the inlet line from making it back to the toilet.

The shorter, straighter and larger diameter the vent line on ANY tank, the less odor you'll have.

And btw, no matter how your tank drains, I'd go with TWO discharge lines...one that goes directly to the deck pumpout fitting, the other goes directly to the overboard discharge pump or thru-hull--which, if the tank is drain via gravity, means that fitting is in the bottom of the tank. That eliminates the need for any valves in the plumbing except for the seacock.

Finally, I strongly recommend that at least once a month you close the seacock and fill the tank about 1/4 full with clean water--sea water is ok--and then open the thru-hull to flush the sludge out of the bottom of the tank and that hose. Put the water into the tank via the deck pumpout fitting 'cuz that sends into the tank at the bottom to stir up any sludge and hold in suspension so it can be flushed out. If you'll do this--and also backflush your vent line every time you wash the boat, you will never have any problems with your system.