Building Logs

Water tanks fitted

Posted by Paul

Plumbing has to be one of the most frustrating things in the build process. It seems that no 2 parts you want to fit come with fittings that fit each other directly, you always need a third adaptor to make the entire part do what you want it to. And each part not only adds cost, its amazing how much plastic costs when it is moulded into a plumbing fixture, but it adds size. And in some of the tighter spaces, and lets face it, when is a plumbing part not in a tight space, that added size makes fitting it a knuckle skinning contortion effort and that’s with the boat in a shed and lids and doors off. Imagine trying to change these parts out on the water. When constructing anything that needs to be serviced, cleaned, or replaced for whatever reason, it has to be as easily accessible as can be, because if its difficult on land, its impossible at sea. Its part of the reason I am building so much redundancy into the boat, 2 of everything I can have. Its one of the great advantages of a cat, 2 hulls, in our rig 2 masts and booms, 2 motors, 2 toilets, and in this particular area of the build, 2 water tanks with all that goes with that (2 tanks, 2 fillers, 2 pumps, 2 accumulators etc). The reason is that if something fails out at sea, there is another to take over its work until such time as a sheltered anchorage or marina is found to do the job in a more appropriate environment.

Its part of the reasoning that goes into any of my choices, including choosing outboards over inboards, so if an outboard fails, you can motor on one motor only until the motor can be more adequately repaired in a safer setting, say on land by a service mechanic in his factory instead of on the boat paying call out rates. The same philosophy is guiding my plumbing fixtures. I have 2 toilets, one with manual as well as electric pump (the ensuite) the other will be electric only but if all electrics fail then the ensuite will still work, if just the main fails (usually just a blockage but who wants to be up to their elbow in it at sea, a real recipe for sea sickness!) we can use the other until we (by we I mean I) can fix it in a smooth anchorage.

And the same follows with the fittings to the 2 water tanks. I had originally thought I would fit 3 x 200 litre self made tanks but decided to go with commercial tanks and settled on 2 x 300 litre tanks running side by side 1200mm fore and aft, 300mm wide and 1000mm deep. In the top front corner of each tank are 4 ports, (so 8 ports in a 600mm wide space) so in each tank 2 are 1 1/2 inch one is 3/4 inch and one is 1/2 inch so double for both tanks, all with fittings coming out of the top all leading forward into the anchor well so its like a spaghetti junction in there. Not sure why imperial is still the size of choice in plumbing but it seems to be. The 1 1/2 fittings are for the filler and the depth sensors I have. The 3/4 is the breather and the 1/2 is the pick up, it has a pipe down the inside so the pick up is picking up from the bottom of the tank. Each tank has 2 baffles. So the unbroken free surface area of any one area is only 300mm x 400mm or just bigger than the surface on a big bucket.


The tank depth guage is a kit bought from Jaycar (Radio shack maybe for the US readers). It comes with all the diodes, resisters and capacitors (I made all those terms up, I have no idea what they are but  they are in the kit) needed to make a sender and the reader. The pvc pipe and 1 1/2 male fitting that screws into the tank you must supply (and it was I that decided the 1 1/2 is what works, I think even 3/4 would have worked but this all fitted so I went with it). And if you want 2 senders, you need to buy the capacitors resisters etc and copper wire needed for the second sender (you get one set in one kit, so if you want a second sender you just buy the individual parts separately, or alternately you could just buy 2 kits and have 2 readouts without the need to switch between senders) and the pvc pipe and top fitting and a 2 way switch so that you can switch between the senders to the same reader. I have a friend that is into electronics kits so I had him make the senders for me (Thanks Dennis). How they work is that the pvc pipe is cut to just short of the entire tank depth and then divided into 11 and 10 holes drilled at each point, through which a copper wire comes out and around the pipe. Inside the pipe is where all the secret capacitors and resistors go, (except in Syria, there the resistors go to jail…..sorry couldnt resist……sorry again!) and each of the copper conductors are joined through the top of the male 1 1/2 fitting to a twin wire like a speaker wire that goes back to the reader. The bottom one travels through the middle of the pvc pipe to the top to be the other wire of the twin speaker wire. The pvc pipe is filled with silicon sealant and you are done. In my case 2 of these wires go back to a 3 way switch next to the reader, one side of the switch being the port tank, the other side the starboard tank and off being in the middle. When switched on an electrical pulse is sent down the wire and to the bottom conductor with one wire and whichever other conductors are still submerged in water in the tank with the other and shorts via the water and shows up as lit LED’s on the reader. A full tank and all light up, an empty tank and only the bottom LED lights up and any combination of however much water is in the tanks and conductors in contact. Simple really. And it is here that the small surface area is important. Because of the movement on the boat, it is possible that the water sloshing around will temporarily light up an led then it would go out as the small water movement clears it. So the idea would be to check water when the boat is calm and to take the lower of any led flashing on and off as the level. And of course, each led shows 10% of the tank which in my case is 30 litres. And at about $100 for 2 senders and the reader its about a quarter the price of a commercial unit. No moving parts so it should be maintainence free and pretty fool proof. And with the reader showing at the switch panel, I can isolate the pumps, turn the manifold taps on and off to send water from one tank to the other and use the isolation switches and the tank depth sender to tell me when to turn the pump off when moving water over from tank to tank. I like to try to make simple tasks as simple as they can be aboard the boat.

The other 1 1/2 female threaded (all the ports are female thread) port is the filler. This is where my fittings and the space I have gets a little complicated and space becomes critical. To be honest I didnt really think this through properly before hand and had to figure it out on the fly. I knew what I wanted but was surprised when I could not just get fittings that fit to do what I wanted without the need for a third piece adaptors to make 2 parts that did what I wanted, fit each other. For example I needed a 90 degree bend and a T fitting to fit each other and for one of them to fit into the female fitting on the tank. They make 1 1/2 female threaded 90 degree bend fittings on each end or one female one male but not one with a male thread on each end. Same goes with the T piece, they only make it with 3 female fittings. So you need a male male thread piece to fit the 2 female (one on the tank one on the bend fitting or one on the bend one on the T) to each other. This adds about 30mm to the height the bend fits at. Same goes for a T fitting. I need a T fitting because I need for the filler to attach to a filler in the deck (at a point higher than the tank) and also for a hose from one of the pumps so that water can be transferred from one tank to the other. And just to add one more complication, on one tank (Port) I need a 3 inlet to send water from the watermaker to the tank.


Watermakers at least the one I will fit, make water quite slowly, I anticipate ours would make about 15 – 20 litres per hour so over the course of a day you might fill one tank about half way. I have no complaint about that. But you would not stand by the watermaker constantly checking that the produces water is not fouled in anyway. In case this happens (for example you could sail through some oil) you dont want your entire water supply fouled. So you produce a days worth. Test it again in your tank and if its all still good, you can pump it out to the other tank and do the same the next day (or in our case probably every couple of days if we are on a longer passage, otherwise we will just use the 2 tanks worth and fill where we can and pickle the watermaker until we need it) when coastal cruising.

The pick up is pretty self explanatory, a 1/2 inch threaded pvc piece with a 90 degree bend, a short section of pipe then a male thread 1/2 inch was fitted into the tank so that a hose to the pump could be easily attached or removed. The 2 pumps will live on the shelf that the anchor winch lives on, inside the top of the anchor well so that should a pump leak it leaks into an already wet well not inside the living space of the boat. The breather also breathes out into the anchor well, the breather pipes fitted so they travel down the wall to about half the depth of the tank. The reason for this is so that should the boat ever end up belly up in the middle of the ocean with a long wait for rescue we would still have access to the water in the tanks. Will never ever be needed we all know that, but it does not hurt to know its built that way. The breathers also act as overflow pipes should we inadvertently walk away while the tanks are being filled, or even if the water maker is left on too long.

The pumps will be connected to 2 3 way manifolds. Dont get me started on those. Bunnings (our big box national hardware stores) carry about 5 brands of 2 way hose splitters and about 5 brands of 4 way but guess how many 3 ways they carry. If you guessed zip you must be familiar with the stockist mentality. Over supply some dont supply the rest. Do gardeners shun 3 ways so much that our biggest chain that has room on their shelves for a wide variety of 2 and 4 way wont carry a single triple? Bizarre! The 3 way manifold will send water from its pump to its hulls faucets, to the other tank or to the other hull via a one way valve to a Y join in the pipe system for the other hull.  The reason again is redundancy. The port hull has main bathroom and the water to the galley also comes from the port system. If the pump should fail, via turning some taps on and off in the 2 manifolds I will be able to make the other starboard pump service the entire boat, or just the port hull if I want and visa versa. Again this is just for the convenience of being able to carry on as normal and switch out or repair the damaged pump at some later time.

The tanks I have are made by a company called Wrengco. I cant speak highly enough about these guys so if you need a tank made these are your guys. I measured the cavity and these guys made the 2 tanks to fit snuggly into the space. When I went down there (Sydney) to pick them up they gave me 2 sheets of 30mm polystyrene foam to lay them on while transported back, and these were perfect for them to sit on inside the cavity to absorb and spread the weight evenly over the deck and reduce the effect of friction and also to insulate them to keep the water cool. I also wedged the tanks in around the sides to ensure they could not move in any direction and when the top is glassed on they wont be able to move in any direction and put a thin polystyrene foam sheet on each side of the tank to surround them in it both to absorb the little movement that the tanks will have when water heats and expands and cools and contracts but also to keep the water as insulated and therefore as cool as possible. Whilst the tanks would now need to be cut out of the boat I have put straps around the tanks in order to make removing them possible, but not only the tank top panel would need to be removed but also the cabin front. I put them there just in case I needed to remove them before glassing them in, but that didnt happen.


Because of the tight space I have to fit the various plumbing into and to ensure later disassembly and  re-attachment is possible I tried a variety of options of putting the elbow first then the T or the T first and then the elbow etc. and the picture on the right is the set up I settled on. It keeps the intake as low as possible to allow for fall to the inlet from the filler spout. But access to these parts is so tight that I will have to put a lid into the dashboard that can be removed in the extremely low likelihood that the pipes need to be removed. This panel will be hidden under whatever  I end up lining the dashboard with (I wont be painting it, I have found a material I quite like but more on that later during final finish phase).


Before fitting the tanks I had a hole in the bulkhead behind them pre drilled and back filled to take an electric cable to go directly from the batteries to the anchor winch in the shortest possible route. The rope in the middle picture is to mimic its placement. The tanks have a natural curved corner and create their own conduit for that cable. After more consideration it will be better for the power to transit to the winch via the switch panel, via the port bedroom. Its a less direct route but means that there is an isolation switch and breaker for the winch with the rest of the power isolation switched. But I did make some use of it, I sent the tank depth sender wires down that route instead. Completely hidden and with 300mm wire to spare!

One final word on the space above the tanks. For a while I had the idea that it might be good to be able to get fresh air into the saloon during tropical downpours, when because of the rain, the hatches would be closed on the cabin roof. It occurred to me that there could be a 100mm high void under the dashboard but above the tanks, and it could be used as a duct for fresh air via the anchor well. With the lid off air would enter the well and be forced down this duct and into the saloon. The anchor well is a wet well so rain getting into it is not so much of a problem and of course on a swing mooring or anchor the bows are to the wind all the time so perfect for directing the breeze into the anchor well. I then decided it wasnt such a great idea, it would require more work in that area of the build and unlikely to be used much and that the space would be much better employed as a sunken open drawer like area where you throw everyday things like keys, mobile phone, tv remote, torch etc. and would get used every day rather than the one day in a hundred that was both hot and wet.

Then finally when fitting all of the tank plumbing it became obvious that the hose clamps attaching the hoses from the deck fillers hosetail to the tank inlet hosetail would be near impossible to undo through the top of the anchor well and a more intelligent solution would be a removable lid to them through the dashboard. Whilst it is highly unlikely that we would ever need to remove the hoses connecting the tanks to the deck fillers, having a removable cover means that if we are stuck in a tropical downpour in sweltering heat we could still use the idea of having the anchor well lid ajar (keeping most of the rain out of the well but letting the breeze in) and having that breeze enter the saloon. Still dont think we will ever open it, but it will be there to be opened. Win win.

Whilst all of this was going on I also had a very satisfying half hours work, where I finally fitted (for size to ensure it actually does fit) the fridge into its space. I need to know it will slide in and out of its space with the cabinet top on before I actually glass it on. If not then I will have to come up with a way to have the top removable (as I did with the bathroom top). It does fit, well almost, it just needs a little rebate in the underside of the front edge of the top to allow for the fridge surround flange without removing the top of the flange (either method is acceptable but I prefer to scallop out the underside of the top and leave the fridge as is) by about 5mm and then it will slide in and out without touching the top. The fridge is one of the most likely things on the boat to need servicing or repair so must be easily removable. It will have 4 screws in the front flange down each side that hold it in place. I have used 25mm ply as the side frame rails so that these 4 screws have a good meaty substrate to grip into. So some time soon I will be glassing the fridge bench top in. And the main kitchen top too. There is no reason now why it cant be glassed in. But forget all that, how good does that fridge look in its place?



Fitting the tanks and glassing in the top was the last impediment to closing the boat up and cutting out the windows. That is next months (March) big achievement so next update should include pictures. It does not seem that much work happened in Jan and Feb and that’s a fair call. Despite being the time of year that I have the most time to throw at the build it has always been a time when I get the least done, both in terms of the hours I actually spend building and the productivity of those hours. The reason (or excuse) for both is the heat. Counting against me this year is the El Nino effect this summer. It has been somewhat cooler, and rained a lot for the first summer since I started building. This should have resulted in me getting more work done. It didnt. I still only managed my average of about 60 hours each month, bringing the total hours so far to about 4200. As always I am hopeful of a more productive month next month and being another step closer to launch. And so with another summer finished, I also pray to the gods of weather that this was finally my last summer building this boat and I enjoy at least as many as I have sacrificed aboard her, starting from next summer.

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3 thoughts on “Water tanks fitted

  1. Greg Smith

    Great looking job on the tanks Paul. The fridge looks fab also. What brand Fridge/freezer is it?
    Regards and best wishes.

  2. Paul

    Isotherm Cruise 200, it has a 50 litre freezer, a 150 litre fridge, runs off 12v or 240v (it self senses when 240v is available and chooses it, so whenever shore power is on it uses that). Specs say it draws about 6 amps but daily use is about 60 amps. It has a Danfoss BD50 compressor.

  3. Henry

    I just spent the last week reading up on your blog. Hat’s off to you on the good work you have done. Your work is inspiring. Glad to know you are entering the home stretch on this. Looking forward to more updates.

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