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The sea toilet.

 For a holding tank design click here.

There are quite a number of different makes of sea toilet and some of them even have electric pump out kits which will convert the basic loo to an automatic flush.

They all use sea water to flush which causes most of the problems with sea toilets. This is because sea water and urine react to produce calcium which builds up inside on all the internal parts and causes the pipes to slowly narrow so that when someone does a ‘brick’ or too much paper is used there is an instant blockage.

Most other problems - which will require stripping the loo down - are caused by people putting things such as sanitary towels or a handful of tissue or other foreign bodies which have not been eaten like cotton buds or matchsticks.

Loo tips

Arriving back in England once again one of the most talked about boaty problems - the marine loo - began to give us trouble. After 30 years living aboard Mo and I have pretty much solved most of the problems.
Many of us yotties have now fitted the standard modern plastic pump loo. Along with many other and older types they suffer from getting stiff to operate and from blocking.
The stiffness is due to a lack of lubrication and the blocking due to the reaction of urine and salt water which produces a calcium build up inside the pump - pipes - holding tank and valves.
In some places an expensive product called 'Head Lube' or something similar can be bought. This is a biologically degradable oil that is simply poured into the pan and pumped through.
A much less expensive solution is to use cheap cooking oil in the same way. This will need repeating every few days.
A longer lasting solution is to clean the system by pumping a little bleach or disinfectant through the system and then removing the pump top located under the pump handle. This gives access to the inside of the pump and the rod and piston / plunger will just lift out. Dry with rag or paper kitchen towel and then grease with a thin smear of silicone grease. This will last for weeks. How to cure the calcium problem next.

 Blocked Loo

The blocked loo is one of the most feared problems of the cruising sailor. It generally happens due to the reaction of urine and salt water producing a calcium build up. This narrows the pipes and coats the valves stopping them working.
If you currently have a blockage then you may well need to dismantle the system to clear it first (YUK) as the following will only help in keeping it clear. It will be unlikely to unblock it and may well make it difficult if you eventually need to dismantle the loo as the acid will be trapped in the system.
The way to keep the system free of calcium is to use hydrochloric acid. In many countries this can be purchased very cheaply from hardware stores or supermarkets.
In the UK our laws make it difficult to purchase chemicals which are freely available in other countries. In France, Portugal, Spain, Italy, Greece etc. it comes in a red plastic bottle and costs around one euro for a litre.
In the UK I have found that garden patio cleaner is strong hydrochloric acid and in this form is easy to purchase.
To keep the system clear I pour the whole bottle (about 1 litre at 30% strength) into the loo pan and then slowly, by giving a few strokes every half hour, pump it through the system.
I do this roughly every 2 to 3 months in an area that is NOT environmentally sensitive as the acid ends up in the sea!
This has virtually no effect on the plastic and metals in the system but will kill off any microbes in a holding tank system.
Some people claim that these microbes can help to stop the holding tank smelling - I prefer not to have blockages!

Lavac sea toilets

These are good sea toilets which use a Henderson type bilge pump for emptying. They have a lid which seals and the pump sucks out causing a vacuum which then causes flushing water to be sucked in. A friend has found that hydrochloric acid attacks a small piece of aluminium in the pump. What he does is to strip the pump and use a domestic loo cleaner to clean the parts.
I did not realise that there were aluminium parts in these pumps, I think think that the recent version is all plastic.
Worth checking if you have a Lavac!!
Another method of keeping the system clear of calcium is to use vinegar. This is considerably more expensive and not as aggressive as hydrochloric acid so may well be OK where there are aluminium parts in the system. Used in a similar fashion to the acid it should help to stop the calcium build up and the need to regularly strip the system.
As far as I am aware all the normal heads such as the almost universal Jabsco plastic pump type only have stainless parts.
Some years ago I tested all these stainless parts from an old loo along with some 304 and 316 bolts by leaving them in 50% strength acid. After 3 days I examined them under a powerful magnifier and found only a slight dulling but no corrosion.
Our current Jabsco is around 6 years old and has not needed the valves or pipes cleaning yet.