New holding tank

[PK123]

I am thinking of fitting a holding tank to my small Mirage 27as per this layout (theres not the room in the bow for a tank and so Im looking at a bulkhead solution). The bottom of the tank would be roughly level with the water line and Ive tried to make the runs (no pun intended!) as smooth as possible.
Any thoughts and observations welcome.

 

[dlochner]

Some quick thoughts.

This will be a gravity drain tank. Keep it simple. There is no need for a direct discharge, just open the the drain to the tank. Gravity will do the work. You will need a pumpout for those times you are in a no discharge zone and you will need to have a valve to prevent the gravity drain.

The head pump should be adequate to lift the stuff to the top of the tank, no need for a macerator.

 

[PK123]

Some quick thoughts.

This will be a gravity drain tank. Keep it simple. There is no need for a direct discharge, just open the the drain to the tank. Gravity will do the work. You will need a pumpout for those times you are in a no discharge zone and you will need to have a valve to prevent the gravity drain.

The head pump should be adequate to lift the stuff to the top of the tank, no need for a macerator.

Thanks Dave - its a pretty small capacity holding tank (but not a big boat) ...the thought process was to have a direct discharge as a back up in case of travelling within the 3m zone with a full tank. But its a lot simpler as per your suggestion ...and less things to go wrong. I may have misunderstood your point about a 'valve to prevent the gravity drain'?

 

[dlochner]

may have misunderstood your point about a 'valve to prevent the gravity drain'?

You have a Y valve below the tank, if you remove the direct discharge then the Y Valve can be a simple ball valve.

As for the small holding tank, you'll just need to find a pump out station or take the boat "for a walk" offshore.

 

[PK123]

Thanks Dave - its a pretty small capacity holding tank (but not a big boat) ...the thought process was to have a direct discharge as a back up in case of travelling within the 3m zone with a full tank. But its a lot simpler as per your suggestion ...and less things to go wrong. I may have misunderstood your point about a 'valve to prevent the gravity drain'?

Makes sense - I guess as well there'd be no need for a venting loop on the 1 1/2 as there'd be the tank vent through which would do the same job i.e simplified as per this https://www.mirtoart.com/image/I0000KBRZYh79ZtU

 

[dlochner]

Makes sense - I guess as well there'd be no need for a venting loop on the 1 1/2 as there'd be the tank vent through which would do the same job i.e simplified as per this https://www.mirtoart.com/image/I0000KBRZYh79ZtU

Yes, this is the design you want. Easy, simple, less expensive.

Also, the vented loop in your drawing was in the wrong place, it belongs on the other side of the Y-valve.

 

[SeaCure]

Many years ago I bought a lightly used SeaRay 270 with a Thedford Porta Pottie hooked up to a macerator and a pump out. The Macerator was illegal somehow in Canadian Lakes so I slammed a cork in it and only used the pump out (every 5 gallons!) That winter I contacted SeaRay who told me the tank position and hose route. Was a nasty job removing washroom walls Helm side panel Seat and remove charger and 2 battery trays, but worth it. The toilet system was now upgraded factory spec. My Jeanneau came with a plumbing system which wasn’t winterized again the manufacturer helped me out. Only the two water tanks survived. Use UL approved gear. Look at a saddle tank behind the toilet. I saw one disguised as a shower seat in a custom steel boat.

 

[DinghySailor]

Yes, this is the design you want. Easy, simple, less expensive.

Also, the vented loop in your drawing was in the wrong place, it belongs on the other side of the Y-valve.

PK123, can you renew the link to your diagram?

I've been searching the site on a similar question. On our boat, the tank is slightly above the Y-valve with a vented line. The previous owner had purchased a manual whale gusher pump for blackwater and never installed it. It appears designed to fit between the Y-valve tank and the thru-hull valve. As we prepare to head into BC waters (!) increasingly over the next years, I assumed I'd need to install the pump to evacuate the tank where legal.

If gravity does the work, I guess the pump is unneeded. Or would a pump somehow be more effective, faster, etc?

 

[Peggie Hall HeadMistress]

For gravity drain to work, the entire tank must be above the boat's waterline...if not, it'll take on water faster than you can dump it when the thru-hull is open. In spec'ing out how high to put it, keep in mind that the toilet has to pump bowl contents all the way up to the inlet fitting on the tank, which is on or at the top of the tank and 4' is the max that most toilets can lift a flush. You'll also need to learn to flush using the dry mode a lot to minimize the volume of run back to the toilet.

--Peggie

 

[Andrew of Oracle]

I have added a couple of valves under the sink of my Bavaria 37 so that I can have the option to use fresh water to flush, this has eliminated the strong sulfur aroma and makes day sailing much more appealing to the whole family . We simply run fresh water into the basin and then pump this into the toilet bowl for flushing, for longer voyages we switch back to sea water , this system also makes it possible to flush both the inlet and outlet lines with a mild bleach or vinegar solution to keep scale at bay

 

[Peggie Hall HeadMistress]

Andrew, you've over-complicated something that's really very simple! And you're using a lot more of your fresh water than you need to.

All you needed to do was re-route the toilet intake line to tee into the head sink drain line below the waterline. This allows you to flush using sea water..then at the end of the weekend--or even at the end of each day--close the drain seacock, fill the sink with CLEAN fresh water, flush the toilet. Because the seacock is closed, the toilet will pull the water out of the sink, rinsing all the sea water out of the intake line, pump, channel in the rim of the bowl and the toilet discharge line.

Never use bleach in the sanitation system--it's destructive to the rubber parts in the toilet...and NEVER EVER combine bleach with vinegar...that'll create chlorine gas, which is lethal! A cupful--2 cups at most--of undiluted distilled white vinegar flushed down the toilet once a week before the boat will sit will prevent sea water mineral buildup in the lines...you can use the sink to do that if you want to. Follow with a clean fresh water rinse after 45-60 minutes. Never leave vinegar sitting bowl, 'cuz when soft rubber (the joker valve in the toilet) is allow to sit and soak in vinegar, it swells and distorts.

--Peggie

 

[Andrew of Oracle]

Hi Peggie
Yes this is what I have don but added a couple of valves to prevent water draining out of the sink, or sea/toilet water coming into the sink when underway ! We sail in some large seas in the Southern Ocean and everything needs to be sealed. Not over complicated mechanics but perhaps my description was bleach is used outside the the “system” vinegar inside, chemistry is always a concise ration on a yacht .

 

[Peggie Hall HeadMistress]

I'm aware that the Southern Ocean is no place for amateurs...Are the seas so large that just keeping the sink drain seacock closed and a rubber plug in the sink while underway not have accomplished the same thing and be easier to use?

--Peggie

 

[DinghySailor]

For gravity drain to work, the entire tank must be above the boat's waterline...if not, it'll take on water faster than you can dump it when the thru-hull is open. In spec'ing out how high to put it, keep in mind that the toilet has to pump bowl contents all the way up to the inlet fitting on the tank, which is on or at the top of the tank and 4' is the max that most toilets can lift a flush. You'll also need to learn to flush using the dry mode a lot to minimize the volume of run back to the toilet.

--Peggie

Peggie, thanks again. For the reason you highlight, I’m back on track for installing the Whale sanitation pump. As I plan this out, I wonder if you (or others) can help me through another related question.

The current blackwater plumbing is this:

• Toilet line to Y valve (a)
• Y valve lines to b) top of tank; c) thru-hull valve fitting (elbowed)
• Separate hose from bottom of tank to deck pumpout fitting.

Question: if I install the pump inline between the Y valve and thru-hull, as instructed by Whale, my configuration has it drawing from the top of the tank, which can’t be right. Will I need to install the pump inline with the deck pumpout line to assure proper suction from tank bottom?

Thanks a head

 

[Peggie Hall HeadMistress]

The current blackwater plumbing is this:

• Toilet line to Y valve (a)
• Y valve lines to b) top of tank; c) thru-hull valve fitting (elbowed)
• Separate hose from bottom of tank to deck pumpout fitting.

Question: if I install the pump inline between the Y valve and thru-hull, as instructed by Whale, my configuration has it drawing from the top of the tank, which can’t be right. Will I need to install the pump inline with the deck pumpout line to assure proper suction from tank bottom?

If I'm visualizing this correctly, you have a y-valve in the toilet discharge line that lets you choose between flushing into the tank or flushing directly overboard.

The only discharge line coming out of the tank comes out of it at the bottom and goes to the deck pumpout. You want to add a line that lets you dump the tank at sea and are asking for the best way to do it.

Jumping to the conclusion that I've gotten all this right, here's how I'd do it:

Instead of complicating the system by adding a y-valve to the pumpout line, repurpose the discharge line coming out of the tank at the bottom to serve the "dump out" pump exclusively and install a new discharge fitting in the top of the tank for the pumpout line...actually fairly easy using a Uniseal UNISEAL and a diptube--a length of PVC pipe that will also double as the hose fitting.

IMO, you couldn't ask for a simpler system. I'll be glad to work out the details with you if you want to send me a PM.

--Peggie