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Nikolina · 19-12-2022, 18:30

I recently purchased a Stiletto 27, a very light weight racing/cruising catamaran. With the board up each hull draws about 9". I'm in the process of installing a head, a small holding tank, thru hulls etc..I would like to eliminate the vented loop/anti siphon and just open and close the seacocks every time the head is used. Anyone see any big issues with this, other than forgetting to open or close the valves? Thanks in advance

ItDepends · 19-12-2022, 19:01

You mean other than flooding your boat if a user has a brain fade?

No other issues at all.

Well, maybe one... if you ever want to sell the boat a surveyor will flag this as a critical issue.

Uncle Bob · 19-12-2022, 19:25

If you plumb the toilet to the top of a properly installed holding tank above the waterline then no vented loop required. Has the advantage of being able to empty via gravity where permitted.

peghall · 19-12-2022, 19:36

I'd install a self-contained system instead of a toilet, separate holding tank and all the related plumbing. I'm referring to an "MSD" 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 the boat to empty it.

A 5-6 gallon model is household height and 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 $300--a fraction of what you'd spend for toilet, tank and all the related plumbing needed. Adding y-valve and overboard discharge pump would allow you to dump it at sea where legal. 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...and a lot less weight if you'r planning to race the boat.

Just an idea worth considering....

--Peggie

massnspace · 19-12-2022, 19:41

What I use in my cat:

https://www.thetford.com/product/porta-potti-565e/

HeywoodJ · 19-12-2022, 20:50

A vented loop is only required if the rim of the bowl is below the waterline. That’s the heeled waterline, although there may not be much distinction in a Stiletto. In practice if the toilet rim is only a few inches above the waterline you might still want one, but once the bowl rim gets more than a few inches above the waterline the bowl itself is your siphon prevention. Given that the Stiletto only draws 9” it is likely that just about any head will have the bowl rim well above the waterline.

Caveat - the bowl can fill to the waterline, depending on where that is and how much water can get in it can be unpleasant when it sloshes around.

Mike OReilly · 19-12-2022, 21:29

Your best option is to install a composting head.

Nikolina · 20-12-2022, 16:46

[QUOTE=peghall;3720510]I'd install a self-contained system instead of a toilet, separate holding tank and all the related plumbing. I'm referring to an "MSD" 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 the boat to empty it.

A 5-6 gallon model is household height and 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 $300--a fraction of what you'd spend for toilet, tank and all the related plumbing needed. Adding y-valve and overboard discharge pump would allow you to dump it at sea where legal. 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...and a lot less weight if you'r planning to race the boat.

Just an idea worth considering....

--Peggie

Peggie,

I have a question about the MSD porta pottys, I didn't even know they existed. How do they rate as far as durability? I'm planning a long trip with several people and the last thing I want is head issues. There will be minimal places available for parts and repair along the way. I have a Raritan PHII and I feel you could flush a brick down it without any problems, plus you can carry spare parts. Also the porta pottys use fresh water flush, I won't have any extra, is salt water okay?