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Old 07-12-2011, 20:01   #16
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Re: Is Gravity Discharge Possible from a Blackwater Holding Tank ?

One more thing: The tank will be higher than the toilet, so you'll need a loop in the toilet discharge line that's a little higher than the tank inlet...and you'll need to learn to flush in the "dry" mode long enough to move bowl contents over the top of the loop if you don't want the a hose that's full of water or waste all the way from the toilet to the top of the loop to run back into the toilet.
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Old 07-12-2011, 20:34   #17
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Re: Is Gravity Discharge Possible from a Blackwater Holding Tank ?

For what its worth - I have an above waterline holding tank and after a few false starts - I am very happy. The tank is custom made to fill a space in the hull - 80 liters - which I consider minimum - otherwise use a Porta Potti. That volume lasts two people three days. Anything less is a WOFTAM - even though expensive production boats have 40 liter holding tanks to meet legal requirements!

I replaced the manual Jabsco Head with a cheap ($200-ish) head from Whitworths (is there one in WA) as mates recommend these - parts are cheap and readily available in Oz. The initial one inch plumbing (head to tank and tank to through hull) proved inadequate and even though head to tank is pressurised by the head pump, paper and "stuff" sludged in the tank and couldn't pass by gravity alone. So I replaced the tank outlet with a 1 1/4 inch pipe, ideally 2 inch would have been better but I couldn't bend and fit larger pipe in a small space. The pump out is on a "T" above the through-hull drain as others have recommended and works well where there are pump out stations!

The below waterline issue was remedied by having a standpipe built into the tank so the head outley fits from below - but there is a chocolate fountain arrangement inside the tank (pardon the imagery). The tank vents to the deck and a clear hose serves as a warning to pump or dump.

I have considered a scientific paper entitled "The sludging properties of commercial toilet paper and contribution on holding tank blockages in yachts." Anecdotally - I concur with others who suggest single thickness good quality commercial paper (I use Delsley - 1000 sheet rolls) as the triple thickness quilted "comfy to your bum" stuff is a disaster! There must be funding for such an environmentally relevant study!

Finally - only poo/wee and good paper and sea water and we haven't had a drama in two years. If we could only manage the calcified sediment that builds up in hoses with urine and salt water - tried vinegar, Coke and I am searching for something that will obviate the need to disassemble hoses and whack them on the pontoon every year... Any suggestions???
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Old 07-12-2011, 22:47   #18
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Re: Is Gravity Discharge Possible from a Blackwater Holding Tank ?

You can avoid clogs if you rinse the holding tank with clear sea water every time you drain it--otherwise the sediment builds up and you will eventually have a disaster. Just drain the tank, then wet flush the toilet with at least 25 strokes, and drain the tank again. Make sure that there are no choke points in your gravity feed system.

You will NOT need a vented loop if the waste discharges into the top of the tank and the tank has a vent--the worst that can happen is that the waste in the line to the tank drains back into the bowl and partially fills it.

As far as capacity goes, we find that an 80 liter tank will last the two of us for a week if we use the toilet only for poop.
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Old 07-12-2011, 23:03   #19
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Re: Is Gravity Discharge Possible from a Blackwater Holding Tank ?

Just remember in ANY system that you come up with the gases that emanate from any holding tank are highly explosive.... ANY VENT should be positioned to vent in a place thats not likely to bleed those gases back into your hull and make sure your gauze in those vents stays in place (itemise into your maintenence checklist), it is the single most important item between having a safe installation and a burnt or destroyed boat.....
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Old 07-12-2011, 23:15   #20
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Re: Is Gravity Discharge Possible from a Blackwater Holding Tank ?

We have a gravity drained holding tank located above the head. It drains via a 65mm waste pipe which is about 90cm long.

We've lived on the boat for over a year and use regular TP - and the setup works just fine. You do have to pump more water through to move everything up the pipe, and we always wait till it's about 3/4 full before emptying to create enough pressure to clear the pipe. The large outlet needs cleaning to keep the barnies under control as an obstruction can block the pipe.

A macerator might be a "nice touch" but everything works fine without it. In fact, having to maintain 5 heads on 2 boats (as above, macerator type & 3 vacuflush) the above setup is without a doubt the most maintenance free.
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Old 08-12-2011, 04:07   #21
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Re: Is Gravity Discharge Possible from a Blackwater Holding Tank ?

Reply to Boatman 61 : I'm looking at the Vetus tanks at VETUS Catalogue 2012 - English
These have a low point at the bottom of the tank that will assist emptying.

Jimbo485, thanks for your encouraging experience.

I'm going to put a Y valve into the system so that I can cover all options. I like the look of the Tru Design Plastics 'Aquavalve' (NZ made) over, say, a Jabsco. Any other suggestions? With double hose clamps on all the joints, is there any need to use a sealant (Sika / 3M)?

Ash aboard 'Unicorn'

In terms of the
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Old 08-12-2011, 10:23   #22
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Re: Is Gravity Discharge Possible from a Blackwater Holding Tank ?

Re Vetus tanks: Surely there are polyethylene tank mfrs in OZ who make a good quality rotomolded or welded plastic tank (avoid bladders!) to your exact specs for less than they cost! Polypropylene is easier to weld...Specify 3/8" walls...fittings (which are spinwelded into any polyethylene tank, but can be cemented into PP) in the sizes and locations that you specify.

Re y-valves: Good quality y-valves have "barrel" inside that the handle rotates to line up a hole in it with the desired outbound hose. Avoid any y-valve that has only a little "gate" that the handle swings to block one side or the other. They leak...and even something as small as grape seed can jam it.

Do NOT use any sealant on any sanitation system hoses connections. Double clamp all hose connections. Warm the hose--being careful not to overheat--and lubricate with dish washing liquid...better yet, K-Y surgical jelly. NEVER use any grease or oil to lube.

Never heat a hose to make it bend tighter than it wants to bend willingly...that will cause the "skin" of the hose on the outside of the radius to stretch and weaken enough to tear...the inside to weaken an possibly kink...not necessarily immediately. Instead, break the hose and insert an inline radius fitting.
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Old 10-12-2011, 16:10   #23
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Re: Is Gravity Discharge Possible from a Blackwater Holding Tank ?

Twenty years. Blake (Lavac) toilet, hand bilge pump dumps waste into top of holding tank (20 gal.), twin 1 1/2" vent lines (per Peggy Hall) using K.O. aerobic bacteria, 1 1/2" line exits bottom, pump out hose tees into bottom hose, waste exits 3" above waterline. Tank is built with WEST System over Baltic birch ply, painted with linear polyurethane.
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Old 11-12-2011, 16:17   #24
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Re: Is Gravity Discharge Possible from a Blackwater Holding Tank ?

Thanks Roy M : you've given me a possible solution if the quotes on HDPE plastic custom built tanks come back too expensive - an epoxy lined ply tank. Looking at the space I'm going to try to use, there are a few angles to contend with and I do want to hang it off a bulkhead, so building it myself will be a better outcome.
Your set up in the bow looks to be a great use of the space.

Ash on Unicorn.
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Old 11-12-2011, 16:27   #25
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Re: Is Gravity Discharge Possible from a Blackwater Holding Tank ?

The drop shelf above the head allows me stand on it to pull a spinnaker or other large sail down below, or to sit on it to take a shower. It folds up to use the head. I use the polythylene tanks only for drinking water. My fuel tanks are also built with epoxy/plywood. They are older than the holding tank and have had zero problems. A couple years ago I drilled out a hole for the fuel sending gauge and the plug smelled like the plywood I built it with years before. The black pump is the saltwater washdown unit with double pumps and accumulator tank. Great for washing the mud off the anchor rode and for spraying boats thirty feet away.
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Old 01-09-2014, 02:48   #26
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Re: Is Gravity Discharge Possible from a Blackwater Holding Tank ?

now that makes real sense. I tried to rod it out when on anchor and having a swim, but there was a L joint to the tank where the rod stopped. I should have tried snaking something up the outlet from the bottom to unplug the blockage. Now I am in harbor in Palermo and no ways going into the water. Is there any chemical that would help?
The thought of telling the girls to dispose of toilet paper in a separate bag would result in mutiny, but I will have to get tough. I've had it with clogged toilets - fished a tampon from the macerator pump the other day - oivey!
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Old 02-09-2014, 06:40   #27
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Re: Is Gravity Discharge Possible from a Blackwater Holding Tank ?

Quote:
Originally Posted by Wild Cherry View Post
The thought of telling the girls to dispose of toilet paper in a separate bag would result in mutiny, but I will have to get tough. I've had it with clogged toilets - fished a tampon from the macerator pump the other day - oivey!
If you don't get the super-plush, multi-layer, extra-fancy toilet paper, then there should be no problem with flushing it. Lots of people do, without any problem. My wife would mutiny, and so would I, if we had to put used toilet paper in a baggie. But we don't. There is just no need, if you use your head properly.

Tampons and "feminine pads" are a whole different matter. Anyone who puts something like that in the head needs to be ordered to clear the clog themselves. One time doing that job and they should be cured of any inclination to do it again.

A lot of people seem to be embarrassed to speak in plain, simple terms when talking about the head. I'm not, because I have had to unclog a head before. So now I make it very clear to everyone onboard... There are four things, and four things ONLY that go into the head:
1. water
2. urine
3. feces
4. the toilet paper that we have provided (and no more of that than necessary)

Period! Nothing else. NOTHING ELSE!

And anyone who violates these rules is going to spend a few hours cleaning out the pump, while I supervise from an appropriate distance.
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Old 02-09-2014, 07:08   #28
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Re: Is Gravity Discharge Possible from a Blackwater Holding Tank ?

Quote:
Originally Posted by Unicorn View Post
Reply to Boatman 61 : I'm looking at the Vetus tanks at VETUS Catalogue 2012 - English
These have a low point at the bottom of the tank that will assist emptying.

Jimbo485, thanks for your encouraging experience.

I'm going to put a Y valve into the system so that I can cover all options. I like the look of the Tru Design Plastics 'Aquavalve' (NZ made) over, say, a Jabsco. Any other suggestions? With double hose clamps on all the joints, is there any need to use a sealant (Sika / 3M)?

Ash aboard 'Unicorn'

In terms of the
I installed a Vetus 25ltr when building my head last year. They are great, solid and the way they are built everything sinks to the outflow.

I got my idea off a boat we hired in the Whitsunday's. Because we don't have to use it much then 25ltr is fine to last a night. We keep the valve open to discharge virtually all the time. And there is no need for a loop above the tank. If I was to recommend a size I'd suggest going as big as you can. The 25ltr is too small unless like mine your not really going to use it as a holding tank.

I recommend a simple Electric head with maccerator, very noisy but work well.

My discharge is an inch pipe.
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