Convert marine toilet to holding tank?

[Alisagc]

So......any guesstimate on cost to turn my marine toilet into one that has the option of going in to a holding tank, or out into open waters. In a '78 O'Day. Right now just going out to sea....but, we plan extensive anchorage and mooring time.

OR - does it make more sense to just go with a port-a-potty or composting toilet?

Thanks for your advice - new boat owners, but experienced campers, RV, compost toilet users

 

[Terry Cox]

Hard to say based upon your posting. How many people on board, how long do you plan on being out each cruise, etc. Our boat came with a 26 gallon holding tank with an overboard discharge feature. We will often be out for two months or more at a stretch with no access to a pump out station.

An estimate of what you need could run $500 in material cost, assuming you did all the labor. Many variables with your boat. You will need a location for the tank, plumbing from the tank to the toilet, a wye fitting to connect to the existing discharge hose, a deck fitting for pump out, etc.

If you plan on just weekend jaunts perhaps a port-a-potty will fill the bill.

 

[Peggie Hall HeadMistress]

On a 25' boat--on any boat under 30', I'd go with an "MSD" version portapotty. The "MSD" designation in the model name/number means it has fittings for a pumpout line and vent line, and is designed to be permanently installed (actually just sturdier brackets than portables, so you could still take it off the boat if you absolutely have to), which means that although it's still called a PORTApotty, you don't have to carry anything off the boat to empty it.
A 5-6 gallon model holds 50-60 flushes...you'd need at least a 30 gal tank to hold that many from a manual marine toilet. No plumbing needed except a vent line and pumpout hose--so no new holes in the boat...and -0- maintenance needed except for rinsing out the tank--which you can do with a bucket while it's being pumped out. Total cost including the pumpout hose and vent line is about $200--a fraction of what you'd spend for toilet, tank and all the related plumbing needed. For just a little more, you could add a y-valve and manual diaphragm pump to also give you ability to dump the tank (only where legal of course). And the best part is, you have all the advantages of a toilet and holding tank without giving up a single square foot of storage space.

Check out the Thetford 550P MSD and the Dometic/SeaLand 975MSD Sanipottie

 

[Alisagc]

Hard to say based upon your posting. How many people on board, how long do you plan on being out each cruise, etc. Our boat came with a 26 gallon holding tank with an overboard discharge feature. We will often be out for two months or more at a stretch with no access to a pump out station.

An estimate of what you need could run $500 in material cost, assuming you did all the labor. Many variables with your boat. You will need a location for the tank, plumbing from the tank to the toilet, a wye fitting to connect to the existing discharge hose, a deck fitting for pump out, etc.

If you plan on just weekend jaunts perhaps a port-a-potty will fill the bill.

We will just be two - anticipating several days up to a week anchored before going out into open sea. We have an existing marine toilet, with just direct discharge - no holding tank.

 

[Alisagc]

On a 25' boat--on any boat under 30', I'd go with an "MSD" version portapotty. The "MSD" designation in the model name/number means it has fittings for a pumpout line and vent line, and is designed to be permanently installed (actually just sturdier brackets than portables, so you could still take it off the boat if you absolutely have to), which means that although it's still called a PORTApotty, you don't have to carry anything off the boat to empty it.
A 5-6 gallon model holds 50-60 flushes...you'd need at least a 30 gal tank to hold that many from a manual marine toilet. No plumbing needed except a vent line and pumpout hose--so no new holes in the boat...and -0- maintenance needed except for rinsing out the tank--which you can do with a bucket while it's being pumped out. Total cost including the pumpout hose and vent line is about $200--a fraction of what you'd spend for toilet, tank and all the related plumbing needed. For just a little more, you could add a y-valve and manual diaphragm pump to also give you ability to dump the tank (only where legal of course). And the best part is, you have all the advantages of a toilet and holding tank without giving up a single square foot of storage space.

Check out the Thetford 550P MSD and the Dometic/SeaLand 975MSD Sanipottie

Ok - that sounds kind of perfect. I like not losing storage! Do you know of any diagrams of the installation with the y-valve and pump?

 

[Peggie Hall HeadMistress]

Enough people have done it that you can prob'ly find a diagram or photo in the forum archives...or perhaps someone can post one. However, it's so simple that you shouldn't need one.

 

[Alisagc]

Great - thanks - I'm pretty comfortable with basic plumbing, etc., so should be easy enough to figure out, sounds like. Awesome tips and information - thanks so much!

 

[Peggie Hall HeadMistress]

There's another rather lengthy thread on this same subject in the smaller boats forum....find the "260 sea toilet" thread.

 

[Alisagc]

Great - I will spend time in that forum, too - thanks so much - been loving going through the different archives, docs, etc.

There's another rather lengthy thread on this same subject in the smaller boats forum....find the "260 sea toilet" thread.

 

[sesmith]

OR - does it make more sense to just go with a port-a-potty or composting toilet?

Thanks for your advice - new boat owners, but experienced campers, RV, compost toilet users

MSD, as mentioned already, is a good choice. If you are partial to composting, check out the C-Head. We have one on our Seaward 25. It works very well for us. You may or may not find you need venting on it. I installed a passive vent on mine and it works fine. No need for any fancy powered vents on the c-head. The c-head will cost more than the msd but less than the other more expensive composing brands.

 

[Alisagc]

We have a portable composting toilet we might use, too - just have to see if it will be ventable on the boat - we will have possession of the boat in early February.

Does a composting toilet meet the requirements of the coast guard and marinas?

 

[Peggie Hall HeadMistress]

Does a composting toilet meet the requirements of the coast guard and marinas?
Yes, but not as easy to maintain on a small boat as on land because they require dry material to soak up liquids and a bacterial product to "encourage" breakdown...all of which has to be stored onboard somewhere. And urine has to be collected separately and disposed of ashore. You also have to keep in mind that composting doesn't happen overnight...it can take a month or more...so most people who empty 'em every 2-3 weeks aren't removing compost, they're just taking waste mixed with dry matter off the boat...iow, emptying what amounts to a cat litter box.

IMO, the simpler the better...and an MSD portapotty is by far the simplest system.

 

[sesmith]

Does a composting toilet meet the requirements of the coast guard and marinas?

In the US, it does. It's classified as a type III msd. In Canada, particularly Ontario inland waters, it may not meet the letter of the law (but does the intent). Coastal waters, no problem. That said, there are many Canadian boats in inland waters with composing heads. We have spent quite a bit of time cruising north of the border with ours without issues.

We use coir in ours (ground coconut husk). It takes up very little space to store, especially when stored in brick form. The urine, as you know, has to be dumped as frequently as your storage dictates. It's really a non-issue for us, as there's always either a marina, or an island or piece of land in the cruising schedule every few days. With the extra storage with the C-head we can go a month before we have to dump the solids. It basically smells and looks like dirt, and I usually just bury it in my yard at home. We've never had any issues with the coir, or had to add anything but coir to the solids container.