Fighting the laws of physics in holding tank installation

[MightyMike]

I've just installed a new 6 gal holding tank and was pleased with my speed in completing the install in just a couple of hours.
Now that it's done, I am wondering if I should slowed down a little bit.
I placed the tank outlets at the top. I hated the idea of effluent sitting in those nice new white hoses from the getgo. My thinking was the high pressure pumpout boat pumps could easily overcome a little gravity and pump that little tank dry. Now I am not so sure.
Also, because our friends at West Marine only had a six gallon tank in stock, rather than the 9 or 12 gallon tank I was planning on, I added a Y valve after the tank to allow for offshore pumping if necessary. I am certain that old Whale Gusher pump is going to have a hard time lifting the waste from the bottom of the tank.
I am now thinking I will at least have to add a tail from the outlet fitting to the bottom of the tank to allow pump out.
Or do I need to change the entire installation so that outlets are on the side of the tank.
Thanks for your help...

 

[SG]

Unless (which I'd doubt) you have a pick-up hose or tube, you need the exit from the holding tank low and the "entrance" high.

 

[Peggie Hall HeadMistress]

If you remembered to put a pickup tube inside the tank that goes to the bottom of it on the discharge fittng, it's highly unlikely that there's a working pumpout in the country that can't pump it out. Without the pickup tube there isn't one that can. But if you failed to add the pickup tube, it's easy to do now...maybe not as easy as it would have been before you installed the tank (it's always cheaper and easier to do anything right the first time), but easy enough. Remove the discharge hose and thread-barb hose fitting. Buy a piece of schedule 40 pvc pipe long enough to reach the bottom of the tank plus enough to PVC cement it into the hose fitting....it needs to be a tight fit, so you might want to take the fitting to the hardware store to make sure you buy pipe that is. Cut the bottom end of the pipe at about a 25 degree angle...any flatter and undissolved TP or waste can get caught under it, any sharper leaves too much in the tank. Insert the pipe into the tank...reattach the hose. That's all there is to it.

Your old Whale Gusher prob'ly only needs a rebuild kit to make it plenty powerful enough to empty your tank at sea.

Hopefully you did install a vent line on the tank to a vent thru-hull? If not, flushing the toilet will pressurize the tank...neither a pumpout nor your Whale will be able to pull anything out of it.

Next project, it would prob'ly be a good idea to ask a few questions BEFORE you start work or even buy anything.

 

[MightyMike]

Thanks, Peggy, for suggestion of the shallow cut on the tail pipe. Left to my own devices, I would have cut it at 45 degrees, leaving more waste in an already tiny tank. I do have a vent fitted, so adding the tail to reach the bottom of the tank should be easy.
You're correct, I should think through projects more carefully, but if I wasn't impetuous, I probably wouldn't have purchased a 37 year old sailboat in the first place.
Thanks for the advice

 

[Peggie Hall HeadMistress]

Nothing wrong with being impetuous...as long as you can afford to be.

I do have a vent fitted, so adding the tail to reach the bottom of the tank should be easy.

Is there a hose on the vent fitting that's connected to a thru-hull (above maximum heel waterline)? If not, you have another easy job to do, 'cuz USCG regs require that all waste tanks be vented to the outside of the boat.

What have you done/plan to do about a toilet?

Btw...I just noticed you're kinda new around here....welcome aboard.

 

[Stu Jackson]

but if I wasn't impetuous, I probably wouldn't have purchased a 37 year old sailboat in the first place.

Aw, c'mon. Really, one has nothing to do with the other, espcecially with something as part of a system that is SO critical. We're here to help. The hardest ones are: "I didn't ask first, I have a mess, what should I do?"

Think about something YOU are good at. How would YOU respond? Other than cordially? : )

Listen to Peggie, she knows.

Good luck on fixing it.

As far as holding tanks are concerned bigger is better. I just cleaned mine out today, Lovely job.

 

[MightyMike]

Nothing wrong with being impetuous...as long as you can afford to be.


Is there a hose on the vent fitting that's connected to a thru-hull (above maximum heel waterline)? If not, you have another easy job to do, 'cuz USCG regs require that all waste tanks be vented to the outside of the boat.

What have you done/plan to do about a toilet?

Btw...I just noticed you're kinda new around here....welcome aboard.

Thank you for the welcome -- and the advice. The previous owner had pulled the old holding tank and re-plumbed a brand new head to direct overboard discharge. So there is an overboard vent. I replaced the old corroded vented loop with a new one. The head is new from last year, so once I get the tail installed i should be all set.
Again thanks for the help.

 

[MightyMike]

My last boat had a 15 gallon tank. It still always seemed to require pumping at just the wrong time. That goes back a number of years. The pump out infrastructure seems so much better now.
I do see the small tank as an experiment. It should cover us for weekend use and my home harbor provides scheduled pump outs twice a week.

 

[Kings Gambit]

A The hardest ones are: "I didn't ask first, I have a mess, what should I do?"

Reminds me of a quotation from the famous statistician Ronald Fisher, which can be here [adapted]: "To consult the statistician [expert] after an experiment [project] is finished is often merely to ask him [her] to conduct a post mortem examination. He [She] can perhaps say what the experiment [project] died of."

 

[Peggie Hall HeadMistress]

he previous owner had pulled the old holding tank and re-plumbed a brand new head to direct overboard discharge. So there is an overboard vent.

That vent is a vented loop (antisiphon device) to which he added a vent line instead of the air valve it should have. It's your TANK that has to be vented to the outside of the boat. That requires a vent fitting on the top of the tank, a thru-hull well above waterline at maximum heel and a piece of hose that connects 'em.

At the risk of appearing to indulge in a bit of shameless self-promotion, I strongly recommend that you get my book...it's available from the online store here (see link in my signature). In addition to solving and preventing odor problems, it's a comprehensive "marine toilets and holding tanks 101" manual that will help you understand how a marine sanitation system works, how it needs to be plumbed, how to maintain it and how to prevent 99% of problems instead of having to fix 'em. And I'm always glad to answer any questions it doesn't.

 

[MightyMike]

Sorry, I wasn't being clear the tank is vented through the hull.
I will let you know how I make out with the modifications
Thanks again for the help.

 

[MightyMike]

To wrap up this thread, I have installed a tail pipe from the outlet located at the top of the tank to the bottom. With the overboard discharge pump I can empty the tank down it within an inch or so of the bottom before losing suction. I expect the deck pump out to reach at least that deep.
Informationly, I was unable to use 11/4 inch schedule 40 as recommended. The outside diameter was too wide to fit inside the 11/2 inch outlet purchased at West Marine.
Fortunately, WM had 11/8 inch flex tubing that fit perfectly and was easy to glue tightly.
Thanks to everyone for their advice and guidance.