The Eventider's News

Issue  Five Autumn/Winter 2005


Page 7.


Holding Tanks


Site Home Page

Page One  Fram update  The Webmaster   Paint Offer  Molly Jade  Scran Bag!

  Dorothy May   Neptune's Nereid update  The Burgee  Events  News

  Back issues - 1  2  3  4

Hit Counter  

Fiddler's Green goes Green!

When we are anchored in a tiny creek, or moored overnight in a marina, or as last year, 2004, enjoying the delights of the inland waters and canals of Holland, I have oft though it would have been nicer on the environment, safer and more convenient, to be able to use our own facilities.  In the marina flushing the loo is not a very nice practice, in tiny creeks it can be equally unsavoury, especially if you fancy a swim!  On many inland waterways it is quite rightly forbidden. 

The added convenience, sorry about that one, of not having to trapse half way round a strange marina in the middle of the night is bliss!

Now having completed the job, ( no not going there!) and even though it has only been really used for 3 months, due to me being crocked, it has been a resounding success.  I wish I had built it in from the start!

The starting place has to be the loo itself.  If you have, as we do, a Lavac, you are nearly halfway there already!  The Lavac used one heavy duty, simple pump, has minimum fuss, no tiny valves and widgets, just a simple sealing lid and seat.  Close the lid, pump the handle and you pump out, creating a vacuum that sucks sea water in via the inlet seacock to flush.  the vacuum is released by a slow leak of air into the suction side hose.  After a short time you can lift the seat to use the loo again.  ( We have also a small fold up sink, emptying via a hose and small valve, into the suction hose, thus into the loo, a couple of strokes on the pump empties the waste water from the bowl. It has the added advantage that the vacuum in the loo can be instantly released by turning the valve under the sink on for a few seconds, thus the loo is back into use immediately, no wriggling whilst you wait for the vacuum to go!)


  First I had to find a place to put the tank.  It had to be a reasonable size, 10 gallons plus, enough for about 5 days for two of us, more if you are selective about what you put in it, if you get my drift!  Measure twice.!!  You could do worse than make a cardboard and sticky tape mock up.  Remember to leave enough room on top for the bends and hoses, 5" in my case.

The space forward on the port side, as close as I could get to the loo compartment was the choice.  In this space I had a spare 3rd anchor, 25lb, 2 gallons of water, 20lb and several lengths of rope.  The anchor was taken ashore, the water and the rope relocated.

I figured that the tank could weigh 100 lb full, but would only be full in marinas, inland or in sheltered water.  At sea it would be pumped dry, so would weigh just a few pounds.  I could live with that.



  Surfing the net, checking PBO then phoning round I found prices for tanks ranged from over 500 to  180.  Guess which one I chose!  Blackwater Plastics, a local company, meant I could drop in to chat, see any problems and get advice.

   Colin and his lad did a good job.  I had purchased all the fittings I needed, hose tails etc, from Lee Sanitation. they also provided diagrams and smell proof hose, (more on that later!)  The inspection hatch meant the top had to be smooth, as the rubber seal was on the outside of the tank.  this meant the top was upside down, as the smooth side is normally inside, to prevent sticking!

  The spacing of the fittings depends on the length of the tails, you have to leave enough room to screw them in, so measure up first.  The outlets, suction pipes, and I have two, (one for onboard pump out, the other for shore pump from the deck),  must go to the deepest part of the tank.  I have fitted a 3/4 inch flush at the other end of the tank.  There is also a hole for a 'Full' gauge, an electric device that lights a small light in the loo when the tank is nearly full.  Cost 50.00, but I thought it worth it

.  Sketch of the top of the tank.  My ideas for placing the fittings.  Compare this to the actual top, a bit different.

The area under the bunk, ply top removed, the 2 gallon container gives an impression of the size, it is also a very odd shape!  I had the tank made to allow for packing it out with foam.


    I used polystyrene foam ceiling tiles!

Glued with Sikaflex, and roughly broken to shape, they were perfect for the job.

    They look a bit rough round the edges, but the tank is well protected.  Don't forget there can be about 100 lb weight in there.

The  pipe fittings are all plastic, BSP thread and sealed with PTFE tape and a smear of Sikaflex.

One very critical point to think of is the max width of any doorways the tank will have to come through.  I carefully measured up the companionway, but forgot there were other doorways!

  Opps!!!  With a little jiggling it will go through, I think! 

  Well it did, other wise I would have had to take the loo door off its hinges!  As it happens I had to take it off anyway later, but do check if you fancy a large tank!

 This is the sender unit for the gauge, it is a simple float switch.

 As with all the fittings, great care is taken to ensure a good seal!  The last thing you want is a smelly leak!!!


Trial fit, the hose tails all arranged to point the right way and the packing, tiles, slid in place.

    The Sender fitted.


It took a lot of courage to use the hole saw on the deck!  A pump out, 1&1/2 inch and a flush, 3/4 inch.  Fittings from Lee Sanitation. The Leading Specialist in Marine Sanitation

 To secure the tank down I used webbing strap, similar to my jackstays... In fact they were once my old ones!  The pic left shows the straps where they cross the keelson on the centre line of the boat, they then go up, over the top and are secured with a lanyard to an eye fixed to the stringer.


    End of webbing, with lanyard fixing.


  Large pre painted ply backing pads, plenty of Sikaflex and a willing helper needed to make up the strength to fasten the deck fittings down.

    Pads in place and fitting offered up, not fixed as yet.

    The tank also needs an air breather, dire warnings are given about the size of this, saying it must be the same size as the Pump out, i.e. 1 & 1/2 inch.  That is crazy.  Even though there is an activated charcoal filter in the little grey plastic tub, there is a free flow of air through it and when you are pumping out there will also be a 3/4 inch flush connector open on deck, so I see no chance of the tank imploding!

        The Pump had to be moved a few inches from it's original position and the direction of the inlet and outlet rotated one flat, easy job, fitting the pipes was not!  It was cold out in the barn and I only had a flask full of hot water, not hot enough!  I ended up boiling pans of water, then it was easy, once the pipe had gone all floppy.  however the odour proof pipe is not anything like as strong as the old spiral wound stuff. I managed to break it several times.  To get more space and leverage I took the loo door off so two of us could get to the pipe at once.  It had a life of it's own!

       The pipe work all in place, I used an awful lot of s/s jubilee clips!  Seacock's double clipped too.  In this pic you can also see the little fold down basin.  the waste pipe has that valve on it that you can operate to release the loo vacuum, very useful.

       Close up of the pump and it's valves.  You have the choice of where you pump from, the tank or the loo and above, where you pump to, the tank or the sea. Once you have that in mind it is no more complicated than before really.  It takes up a little room on the bulkhead,  but does not protrude any more into the compartment than it used to, so elbow room is the same.

  Looks like a plumbers nightmare, but I have used a few plastic pipe clips since to pull the pipes closer in to the sides.  none of the fittings at the back 'get in the way', as they are behind the loo!     

    At the tank end, pipes had to be lead through holes in bulkheads  and out of harms way.

     Hose clips in place, all strapped down.

      Bunk top replaced and screwed back down.  there is a small space above the tank, but not really a storage space.

         You would not know the tank was there would you!

    With all back in place, and the loo having been tested, filled and emptied, pump worked in all directions, all works like a dream.  I used 90 degree bends near the pump, to fit it in the space, it would have been better to use swept bends, but they would not fit.  So far we cannot find a fault with the system.  I would recommend it to everyone.  It certainly gets Darian's vote, no more tripping up to the loo at night in the Marina!


I would recommend Lee Sanitation, they have their own website,

They  publish drawings of all different setups for tanks, but having a Lavac helps, you already have the pump!


John Williams