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Portapotty or holding tank on a Tanzer 8.5

4901 Views 6 Replies 5 Participants Last post by  canadianseamonkey
I recently purchased my Tanzer 8.5 it currently has a portapotty installed but the previous owners mentioned that it used to have a macerator.Now my question is does anyone know 1.Is there a holding tank already installed somewhere(if there is i can't locate it),2.If there is a holding tank why isn't there a topside pumpout valve(i did find a sealed thru hull fitting behind the porta that roughly one foot or so above the water line and what was possibly a thru hull fitting also sealed below the waterline also behind the porta)3.If there is no holding tank how difficult would it be to install anew head with a holding tank and any recomendations on type of head or size of tank to install and would i have to haul her out to do the install? I would greatly appreciate any help with this as it is probably going to be the first decent size project i'll be doing on her.We currently liveaboard in a marina and the porta is just a royal pain in the a*s.thanks again for any help.:confused:
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On one 35' boat i race on we went with the 6 gallon porta potie with a deck pumpout VS doing a new holding tank

The holding tank is only going to allow longer times between pumpouts as at least around here its pumpout ONLY
thanks for the info Tommays definitly easier than installing a whole new system

The T8.5, if so equiped, will have a shaped holding tank located below the v-berth, and you would be able to see this by removing the access panel on the top of the v-berth, underneath the cushions. If you do not find one, then look in the anchor locker for the manufacturer's pumpout fitting.

The marine head unit sits on the raised floor section in front of the port side hanging locker across from the sink. There should be a single thru-hull low and forward on the port side in the v-berth cavity for the raw water intake for the flush. If there was a macerator, it would have a thru-hull for the out flow and wiring to support the electric motor. All of these would be below the waterline.

On the original install, the toilet out-hose went to a fitting on the top of the tank, and a hose went from a fitting on the bottom front of the tank to the pump out fitting in the anchor locker. Additionally there would be a single small vent fitting high out of the water and near the bow as a holding tank vent.

Tommays is correct that all a dedicated holding tank will give you is the ability to go longer between pumpouts. I also know of people who have your arrangement with a fixed pumpout fitting. In my juristiction a macerator and over the side pumping is illegal and thus not an option. Thus if you want to be able to stay out as a couple for several days on the hook exploring your local sail area then a larger holding tank is a necessity. It certainly proved so for us.

As the 1981 T8.5 we purchased had a broken head, and the tank and hoses had over the years become permeated, we replaced the lot with new, a larger tank, and a second tank vent to reduce odors by allowing air to get into the tank more readily. This eliminated the head smell in the boat and was money well spent.

An alternative to a hard tank for black water is a holding bladder. This requires no vent hose as it expands and contracts as the volume of the contents waxes and wanes. It is not a recommended option (although I know of at least one boat that uses it) because the rolling action of a boat under sail causes the bladder to move; leading to chaffe and the unpleasant result you would expect.


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To continue, the install is not that difficult, but not without issues. Getting a standard Jabsco marine head will prove a simple intall on its own. How difficult the job then becomes depends on your choice of tank size. Bear in mind that the original tank was a custom job designed to fit the space. It was sized to be dropped into the v-berth through the cutout made by the manufacturer in the top of the v-berth, and had a multi-faceted bottom shaped to fit securely against the severe v-bottom of that area of the hull.

I found it not possible to get an exact fit, and I wanted greater capacity. I needed to cut a larger access hole, and then for the install I covered the area of the hull where the tank would rest with wax paper and the tank with tinfoil. This allowed the positioning of the tank and the connection of the hoses and then to expanding-foam the voids between the new tank and the hull to ensure that the tank would be fully supported as the contents will weigh a lot when near full.

It was a bear to attach the sanitary hose, as these are a very tight fit. My solution was to keep handy boiling water in which I could emerse the hose end to heat and soften prior to forcing on to the tank fitting.

Do you need to haul out to do this job? If the existing thru hulls have working valves, then the raw water input hose can be connected to one of these and then to the head input. As to the rest, all othe rholes are above the waterline and hence no haulout should be required.

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I don't believe a macerator necessarily means there was a holding tank - in "the bad old days" before we stopped tolerating water pollution, many boats' heads simply pumped out to sea. Could that have been the case with your Tanzer? It would explain the lack of a pumpout deck fitting.

You don't mention the size of your porta-potty or how often you have to dump it out ... but the biggest portable I've seen (mine) has a five-gallon holding tank. That's not a lot of used beer, but it's a lot of "stuff" to carry ... and to pour, oh-so-carefully, into the marina toilet. Bad enough after a long weekend, but every couple of days on a live-aboard...?

When I was shopping for my current boat, I saw one with a "super-potty" that might meet your needs. This was a one-piece unit, with a china bowl perched on top of a 9.5-gallon holding tank. (Dometic makes it, their 711-M28 marine sanitation system.) It would be almost as easy to install this as it would be to plumb a deck fill onto a porta-potty. (It does use fresh water to flush, but Dometic says it uses only about a pint per flush and that it has an integral vacuum breaker to protect your water supply.)

If you have a five-gallon porta-potty, this will hold about twice as much and need to be pumped out about half as often. It is, however, more than three times as expensive (West Marine 2009 wishbook: 5-gallon porta-potty = $160, Dometic 711-M28 = $569). And it's bigger - the tank is about 19"x19" square, and the bowl stands 20" high. (I saw one in a MacGregor 26X I was thinking of buying, and it didn't leave much leg or foot room in that boat's head compartment - but you may have more legroom in your Tanzer. I'd make a box and see.)

Maybe this will help?

Good luck,
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I'm not sure where you are sailing, but porta-potties are not legal in Ontario Canada. So if you plan on sailing in most parts of the Great Lakes you'll need a proper system.

Protecting the Marine Environment - A Boater's Guide - Office of Boating Safety - Design, Equipment & Boating Safety - Marine Safety - Marine Transportation - Transport Canada
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