diy holding tank

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saltyrob

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Hi Folks,

With a bit of luck we may be able to hang onto the boat for another year, although it will take economies in other areas, maybe christmas dinner and lights on Economy 7 and sharing bath water with neighbours.Anyway we hope to sail to Holland again and I have been thinking about building my own small holding tank,has to be smallish as boat only 8.3 metres and space at premium.Open to any suggestions and sources of information on installations.Would stainless steel be a possibility as have access to welder.

Many thanks

Robert
 
What I have done for the last couple of years is to use a Porta-Potti - much cheaper than fitting a holding tank with all the associated pipework, valves etc.
It just gets used on the Dutch Inland waterways, easily emptied at most marinas.
Even though I have a 10m boat I still consider this to be the cheapest solution until I get round to fitting a permanent holding tank at some time in the future.
See eBay - this is an example for £55 delivered and it's new.
http://cgi.ebay.co.uk/Toilet-Porta-...ervan_Caravan_Accessories?hash=item230464de70
 
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For information on different layouts of holding tanks goto www.leesan.com or www.tek-tanks.com Both make tanks and supply fittings. Other good sources are www.vetus.co.uk and www.jabscoshop.com

The simplest is a gravity tank, provided you have room above the waterline close to the loo and outlet. You need to get at least 30 litres and have a pump out through deck. avoid stainless steel as uric acid is not kind to welds! Plastic is much better and a custom made tank is not a lot different in price. Whatever layout you use, budget for at elast £500 - more if you go for a pumped system.
 
saltyrob said:
Hi Folks,

With a bit of luck we may be able to hang onto the boat for another year, although it will take economies in other areas, maybe christmas dinner and lights on Economy 7 and sharing bath water with neighbours.Anyway we hope to sail to Holland again and I have been thinking about building my own small holding tank,has to be smallish as boat only 8.3 metres and space at premium.Open to any suggestions and sources of information on installations.Would stainless steel be a possibility as have access to welder.

Many thanks

Robert
Click to expand...

PM'd you.
 
I know folk who've used Tek Tanks before & speak highly, though I too am going to opt for Porta Potti, for economy, simplicity & less hassle emptying. Best price I've found so far for the larger model, which has 21 litre holding tank here, budget model only 50 quid from ebay. The larger model is taller as well so you don't have to bend down so far, brilliant! And I have no connection to Thetford!:D
 
Holding Tank material

I have a friend whose original equipment Stainless holding tank failed in four years. Hydrogen sulphide from fermenting poo rots stainless fast.
You can get a small tank (c. 5 gallons)at a high price which is designed to fit round an RM69 ? marine loo. It also fits round a compact Jabsco loo.
The diverter valve in this system has close tolerances so needs watching. I spent a smally afternoon cleaning up the valve when it got chalked up a year or two ago and have not forgotten. The advantage of this system is that it occupies little space and the plumbing is simple.
 
DIY tank

Building a holding tank or any other tank is simple and not expensive, they can be made to any shape or size with a little DIY know how and common sense.

I use closed cell foam, Micro-fibres and Micro-balloons, standard and epoxy resins. Using foam has the advantage that the tank will not sweat or form condensation because of it's insulation properties.

Start by cutting the foam to form the required shape, any curves can be achieved by cutting the inside of the curve / foam with a standard hand saw, simply cut slots across the required curve area, the more curve you need the closer the saw cuts, you can even compound the curve by cutting both ways or at a angle.

Once you have the foam cut, fill the saw cuts with standard resin and micro balloons and bend to the required shape, wiping off any excess material to leave a smooth internal finish.

When all sides are ready, apply some micro fibres at the joints and clue the tank together leaving a 3 mm thick layer of glue between joints and the top off to allow access to the internals.

Again wipe away any internal excess material, but this time use the back of a spoon to form neat rounded corners, this will prevent hang up in the tank as well as make it stronger and easy to clean.

Next apply 3 coats of 250 Gram chopped strand mat with a standard resin, also include the lid in this covering with glass. Then do the same on the outside after rounding off the all edges and corners, don't fit the lid yet but you can glass it.

Next fit any pipes and fittings you are going to need and make sure you seal the foam exposed when cutting with a mix of micro fibres and use Epoxy resin for this, when all fittings are done coat the inside of the tank but not the top edge with 4 coats of epoxy resin wet on tacky to avoid sanding between coats.

You should now have a tank fully glassed and fitted out but no lid on.

Turn the lid over so the inside is facing up, measure the inside edge of the tank and glue down some strips of foam to locate the lid, these can be stuck down using standard resin and micro fibres provided you have not applied epoxy resin to the top edge of the box, if you have then use and epoxy resin.

These strips are to locate the tank lid and also to prevent any glue dropping inside when we glue it on.

Check the fit after curing and make any adjustments if needed and epoxy coat the new strips and the underside/inside of the lid only as above wet on tacky, no need to wait for this cure, add some Micro fibres and epoxy resin around the lid and place into position, no need to press too hard, just enough to leave a 3 mm or more layer of the fibres between lid and box.

Wipe away any excess glue because this will be very hard to sand off after it cures.

You now have a tank with all the required fittings, you may want to pretty up at least the areas that will be visible. To this just apply some micro balloons and standard resin over the area with a straight edge to fill in the small lows between the fibres, let this cure and sand flat with a block and a 250 grit paper. clean off the dust with a little acetone and apply a coat of flow coat (standard resin and pigment). faster if rolled on with a 80 mm wide medium nap roller, you can tip it with a brush if you like but it will self level.

There you go, a new tank with good thermal properties that is custom made to fit and looks great, will probably outlast the boat.

I hope this helps.

Avagoodweekend......
 
I like the idea of a Porta Potty fitted with an elbow under the tank and a diaphram type bilge pump via a swan neck to an u/water skin fitting. Only problem if extended cruising inland.Perhaps a Y valve to a simple tank for marina pumping out?
A
 
Having used a porta potti type asthe main heads on a boat they work well and the chemicals seem to work OK with salt water too. We carried one on the present boat for the transit of the Forth and Clyde Canal as we had not by then installed a proper holding tank. Depending on the space available another consideration for permanent installation would be a Thetford cassette toilet. All they are are permanent porta pottis with a removable **** tank.
 
In your position I would be tempted to adapt a plastic jerry-can (excuse the unintended pun).
The holding tank on a boat which has just acquired me has a six US gallon holding tank which satisfied the Florida coastguard who issued its certificate.
 
oldsaltoz said:
Building a holding tank or any other tank is simple and not expensive, they can be made to any shape or size with a little DIY know how and common sense.

I use closed cell foam, Micro-fibres and Micro-balloons, standard and epoxy resins. Using foam has the advantage that the tank will not sweat or form condensation because of it's insulation properties.

Start by cutting the foam to form the required shape, any curves can be achieved by cutting the inside of the curve / foam with a standard hand saw, simply cut slots across the required curve area, the more curve you need the closer the saw cuts, you can even compound the curve by cutting both ways or at a angle.

Once you have the foam cut, fill the saw cuts with standard resin and micro balloons and bend to the required shape, wiping off any excess material to leave a smooth internal finish.

When all sides are ready, apply some micro fibres at the joints and clue the tank together leaving a 3 mm thick layer of glue between joints and the top off to allow access to the internals.

Again wipe away any internal excess material, but this time use the back of a spoon to form neat rounded corners, this will prevent hang up in the tank as well as make it stronger and easy to clean.

Next apply 3 coats of 250 Gram chopped strand mat with a standard resin, also include the lid in this covering with glass. Then do the same on the outside after rounding off the all edges and corners, don't fit the lid yet but you can glass it.

Next fit any pipes and fittings you are going to need and make sure you seal the foam exposed when cutting with a mix of micro fibres and use Epoxy resin for this, when all fittings are done coat the inside of the tank but not the top edge with 4 coats of epoxy resin wet on tacky to avoid sanding between coats.

You should now have a tank fully glassed and fitted out but no lid on.

Turn the lid over so the inside is facing up, measure the inside edge of the tank and glue down some strips of foam to locate the lid, these can be stuck down using standard resin and micro fibres provided you have not applied epoxy resin to the top edge of the box, if you have then use and epoxy resin.

These strips are to locate the tank lid and also to prevent any glue dropping inside when we glue it on.

Check the fit after curing and make any adjustments if needed and epoxy coat the new strips and the underside/inside of the lid only as above wet on tacky, no need to wait for this cure, add some Micro fibres and epoxy resin around the lid and place into position, no need to press too hard, just enough to leave a 3 mm or more layer of the fibres between lid and box.

Wipe away any excess glue because this will be very hard to sand off after it cures.

You now have a tank with all the required fittings, you may want to pretty up at least the areas that will be visible. To this just apply some micro balloons and standard resin over the area with a straight edge to fill in the small lows between the fibres, let this cure and sand flat with a block and a 250 grit paper. clean off the dust with a little acetone and apply a coat of flow coat (standard resin and pigment). faster if rolled on with a 80 mm wide medium nap roller, you can tip it with a brush if you like but it will self level.

There you go, a new tank with good thermal properties that is custom made to fit and looks great, will probably outlast the boat.

I hope this helps.

Avagoodweekend......
Click to expand...

Excellent post, with really useful tips and info. I've taken the liberty of saving it in my Technical folder.

Thanks for that.

Vyv
 
vyv_cox said:
Excellent post, with really useful tips and info. I've taken the liberty of saving it in my Technical folder.

Thanks for that.

Vyv
Click to expand...

Your welcome Vyv.

I forgot to mention if you use any PVC pipe it can be problem getting a good bond, however if you heat the pipe with a flame it will form small black balls and bond well, have a couple of practice runs first, the heating must be rapid so you don't deform the pipe.

Avagoodweekend......:)

.
 
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Re bonding PVC pipes. Not for a boat, but we used to put a generous coat of glue on, wait a couple of minutes and roll the tube in sand. For bonding into pools and other water tanks this worked well.
A
 
DownWest said:
Re bonding PVC pipes. Not for a boat, but we used to put a generous coat of glue on, wait a couple of minutes and roll the tube in sand. For bonding into pools and other water tanks this worked well.
A
Click to expand...

Thanks, I will try this method on a test bed and test to destruction and compare the results with the burn method.

Will let you know the outcome.

Avagoodweekend......
 
oldsaltoz said:
Building a holding tank or any other tank is simple and not expensive, they can be made to any shape or size with a little DIY know how and common sense.

I use closed cell foam, Micro-fibres and Micro-balloons, standard and epoxy resins. Using foam has the advantage that the tank will not sweat or form condensation because of it's insulation properties.

Start by cutting the foam to form the required shape, any curves can be achieved by cutting the inside of the curve / foam with a standard hand saw, simply cut slots across the required curve area, the more curve you need the closer the saw cuts, you can even compound the curve by cutting both ways or at a angle.

Once you have the foam cut, fill the saw cuts with standard resin and micro balloons and bend to the required shape, wiping off any excess material to leave a smooth internal finish.

When all sides are ready, apply some micro fibres at the joints and clue the tank together leaving a 3 mm thick layer of glue between joints and the top off to allow access to the internals.

Again wipe away any internal excess material, but this time use the back of a spoon to form neat rounded corners, this will prevent hang up in the tank as well as make it stronger and easy to clean.

Next apply 3 coats of 250 Gram chopped strand mat with a standard resin, also include the lid in this covering with glass. Then do the same on the outside after rounding off the all edges and corners, don't fit the lid yet but you can glass it.

Next fit any pipes and fittings you are going to need and make sure you seal the foam exposed when cutting with a mix of micro fibres and use Epoxy resin for this, when all fittings are done coat the inside of the tank but not the top edge with 4 coats of epoxy resin wet on tacky to avoid sanding between coats.

You should now have a tank fully glassed and fitted out but no lid on.

Turn the lid over so the inside is facing up, measure the inside edge of the tank and glue down some strips of foam to locate the lid, these can be stuck down using standard resin and micro fibres provided you have not applied epoxy resin to the top edge of the box, if you have then use and epoxy resin.

These strips are to locate the tank lid and also to prevent any glue dropping inside when we glue it on.

Check the fit after curing and make any adjustments if needed and epoxy coat the new strips and the underside/inside of the lid only as above wet on tacky, no need to wait for this cure, add some Micro fibres and epoxy resin around the lid and place into position, no need to press too hard, just enough to leave a 3 mm or more layer of the fibres between lid and box.

Wipe away any excess glue because this will be very hard to sand off after it cures.

You now have a tank with all the required fittings, you may want to pretty up at least the areas that will be visible. To this just apply some micro balloons and standard resin over the area with a straight edge to fill in the small lows between the fibres, let this cure and sand flat with a block and a 250 grit paper. clean off the dust with a little acetone and apply a coat of flow coat (standard resin and pigment). faster if rolled on with a 80 mm wide medium nap roller, you can tip it with a brush if you like but it will self level.

There you go, a new tank with good thermal properties that is custom made to fit and looks great, will probably outlast the boat.

I hope this helps.

Avagoodweekend......
Click to expand...
When you say foam, do you mean squeaky polystyrene?
Stu
 
skipper_stu said:
When you say foam, do you mean squeaky polystyrene?
Stu
Click to expand...

No Stu,
Poly resin will reduce polystyrene foam to a sticky liquid. There are many foams of many types suitable for use with both poly and epoxy resins.

Closed cell foams will not take up any moisture like many that turn into a mush when exposed. You can often purchase small off cuts from local boat builders or yards though.

Hope this helps.

Avagoodweekend......:)

.
 
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