2018 NC 795 - Holding Tank question

[rob2020]

Emptying the holding tank using the valve located in the bottom of the bilge. How does it work do I just turn the valve and gravity does the rest. Previous boats have pumps macerators. Not sure how it works because the valve is below the waterline.

[rene460]

Hi Rob,

This question is appearing in different threads, but I will have a go at answering here.  Marine toilet systems are very similar in all models and brands, both power and sail.

Basically, yes, when you open the big valve in the bilge, gravity does the rest, especially if you have a mascerator.  But even without, so long as you and your crew and visitors avoid putting the wrong stuff down the toilet.  Remember, nothing that you didn’t eat first, apart from moderate amounts of toilet paper.  And my brother says in the case of cherry pips, not even when you have eaten them first.  I don’t even want to ask how he knows that.

But a plea for consideration for your fellow water users, not in the marina, rivers channels lakes, but preferably only well off shore.  

There is another normal facility, which I hope you have but you will have to have a closer look to see what you have.  Other 795 owners may come in and tell you what they have.  Many boats also have a deck pumpout connection which allows a shore based vacuum system to empty the tank into the land based sewer system.

This system has a deck plate similar to the fresh water tank inlet and fuel inlet, so read the labels carefully.  This outlet has a tube which goes straight down to near the bottom of the tank, hence the deck plate has to be directly above the tank, not hard to find.  If the boat is new, the deck plate may be attached by a chain.  You need to remove this chain and screw in a standard Camlock coupler to use the system.  The shore hose connects to the coupler, check the instructions to ensure that any valves on the shore unit are in the right place and turn the switch.  Once the pump has done its job, I put about 50 pumps of clean water through the toilet and pump again.  The tube does not reach the bottom of the tank, so this procedure at least helps dilute the remaining quantity.  I carry my own coupler to minimise the risk of the supplied one being missing or the threads damaged.  I keep it in a screw top container with a little disinfectant.  Obviously a good supply of disposable gloves come in useful for the task.

We sail on a lake system, and dumping is definitely unsociable and discouraged.  In some countries it is just straight illegal.  But there are pump out stations at several locations around the lakes, even two floating barges where you have to pump the handle by hand.  

Have a good look around the tank, usually the top has three connections, the inlet from the toilet, a vent hose and a pumpout connection.  For various reasons you will become quite familiar with the workings of a marine toilet before very long.

rene460

[Charlie-Bravo]

And .... as I have now finished eating, as you have already noted , some of the plumbing is below the waterline and although a gravity flow will empty 'most' of the tank contents you will have a mix of sea water and tank contents more or less up to the water line. this is where the chemistry starts, as sea water and urine when mixed and left to stand will pong, and also calcify in the pipes, this eventually crumbles and tries its best to make the valve jam ..... the pong , given some time will permeate through the pipework giving a very common boaty heads smell, most unpleasant.

Our remedy has been to freshwater flush, and before leaving the boat, load the tank with non enviro friendly chemicals, then empty the tank ( well off shore ) closing the valve just before the emptying is complete, so no sea water is left in the pipes.
Sounds like hassle, but it does keep things smelling sweat and fresh in our boats.

CB

[rob2020]

Thank you all for the response is definitely helpful. The boat is not equipped with a macerator generally I only emty the holding tank if I'm many miles out in the ocean never in the lake or Rivers.

[rob2020]

I guess related question I noticed the holding tank does not have any sort of filter to the vent like previous boats.

[rene460]

Hi Rob,

Our SO30i does not have a filter in the vent either.  Doesn’t seem to be a problem.  One less thing to block.  Our neighbours in the next pen are in a very small boat, with the cockpit normally about 3 ft from our vent.  They spend a lot of time in the cockpit, and we know them well enough that they would say something it it was a problem.  I suspect the air intake when the tank is emptied plus the normal breathing due to daily temperature changes keeps enough oxygen in the tank.  The splash return from the inlet at the top of the tank probably helps mix the air into the liquid, at least a little.  Just a simple tank, yet such complex processes once we add the sewage.

As far as I can understand, it is the anaerobic decomposition of the sea creatures, algae etc that come in the sea water that is responsible for the smell.  The compounds in urine certainly are responsible for the scale, and possible also the smell.  Similarly with the normal sewage composition.  So long as there is plenty of oxygen and a suitable chemical treatment, the tank contents do not seem to be too much problem.  We add a compound that claims to promote biological breakdown rather than just the normal poison to kill the pathogens.  I can never remember the name, but it’s made in Brisbane so probably not available in other countries, where no doubt there are local similar products.

When you open the drain while out at sea, it only drains down to sea level, so you should not get too much seawater in unless it is rough conditions.  But my procedure in that case would still be to shut the valve, 50 or more pumps of clean water then opening the valve again to dilute and flush a bit more out of the bottom pipe would still help.

We went to fresh water flush by the simple method of using the hand basin/shower head to supply the water to the bowl, and extra when we leave the boat to make sure the hose is mostly fresh water.  It definitely stops the smell in the head due to the decomposition of the critters in the incoming sea water while we are on board and the system is in regular use, and definitely helps reduce the problem when we are away, and may reduce the scale.  It has been hard to tell with the scale, and we seem to have some swelling of the inlet valve rubber to the pump, so have had to do the service a couple of times anyway.  Probably the cleaner we use, but hard to tell when first a road trip, then bushfires and now COVID have disrupted our normal routine  and it all becomes hard to keep track of.  I am hoping that eventually I will see a scale reduction.

rene460

[rob2020]

Thank you for the tips I will definitely take those in mind.

[bereboot]

I think that vinegar stops/dissolves scale build up.
Pump it through the system a few times during the season, and let it rest for a few days.

[sleighride]

Practical Sailor does not recommend vinegar for heads, but suggests both Raritan’s CH (cleans hoses) and it’s CP (cleans potties) which I have found to be effective for the last two years. The CH product is most effective for scaling, but is hard to find in marine stores in US, and so I order on line. It is non toxic and biodegradable! A bit expensive however😩

[julian]

Slight diversion from this thread...I have just taken ownership of a Jeanneau Sulight30. The head flushes with sea water and works perfectly.  However, there is no holding tank and I would like to fit one.  Has anyone any recommendations on a suitable tank to purchase?