Holding tank material

Either plastic or fiberglass. The acids will destroy any metal tank way before its time. Plastic should be less expensive as well. Thicker plastic is better.

ps Island Packet used to use aluminum for holding tanks. If they were used they were replaced eventually because of leaks.
 
galadriel said:
Your right about being cheaper, the 316 stainless looks more robust though.
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A very well made 316L tank, using all the correct filler rod materials, may last reasonably well. These pages have seen complaints of very many that didn't. Lee Sanitation make theirs from high density polyethylene, Tek tanks use polypropylene. Both will last pretty much indefinitely. One made of glass reinforced epoxy would probably be pretty good if well constructed.
 
I wouldn't trust stainless steel for a holding tank. Great for water anf fuel tanks though. The corrosion from effluent would eventually cause corrosion in a weld. The other advantage of plastic is that there are hundreds of stock sizes and you can have the fittings placed exactly where you wish. And all for less.
 
The welds in stainless sometimes get pinhole leaks from fuel or water over time. Add uric acid and you will have a real problem. If you go with stainless ask for a written 20 year guarantee. You should easily get that time out of good plastic. (But you'll never get the guarantee.)
Many have gone before you with metal holding tanks including respected builders. All have seen the problems.
 
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galadriel said:
Whats the opinion of the poo advisers, stainless steel or plastic for a holding tank?
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"The headmistress" a one time active contributor to these forums and acknowledged expert advocates 3/8" molded (sic she's American) seamless polyethlene, and poo-poos metal tanks of any sort.

Tek tanks do them, and I'm sure many others.

Interesting that AFAIK all the Swedish marques install stainless tanks.
 
mitiempo said:
I wouldn't trust stainless steel for a holding tank. Great for water anf fuel tanks though. The corrosion from effluent would eventually cause corrosion in a weld. The other advantage of plastic is that there are hundreds of stock sizes and you can have the fittings placed exactly where you wish. And all for less.
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Does anyone make these plastic tanks strong enough to mount the loo on directly saving a plinth and making it easier to find room for the tank ?

Boo2
 
Definitely plastic - either rotationally moulded to a standard size or more usually welded as per Tek Tanks because most boats need a custom shape. SS a no-no because the welds do not like uric acid. The added advantage of plastic tanks is that you can see the contents level, particularly on bulkhead mounted tanks and also it is easy to add mounting lugs to attach to the boat's structure. Most new boat builders now use plastic - if they have the volume like Bavaria they can have them moulded, but low volume builders use fabricated tanks.

BTW just because some Swedish builders use SS does not mean they are right as some owners have found out! (like many of their building practices they are not necessarily the best).
 
As Tranona posted plastic lets you see the level. ABYC calls for a method of knowing when the tank is 3/4 full so this requirement is met. Whatever material you do have to know when it is getting close to full.
 
I have several poo tanks over the years and never had any problems using a foam core and epoxy coating on the inside only.

Foam core MUST be closed cell, construction is simple and fast, can be any shape or size, with or without baffles.

Adding pipe fittings is simple as is inspection covers and level indicators.

The big advantage of foam is that it will not sweat, form condensate on the outside due to temperature differences. The epoxy lining provides a very good chemical barrier as well.

Well within the average DIY salty.

Hope this helps.

Avagoodweekend......:)

.
 
When you have fitted your holding tank, you may need make a point of operating the large drain valve regularly. The acids etc in the tank may cause this to seize up in only a few weeks otherwise.

Happy to show you mine on 14th May!
 
galadriel said:
Whats the opinion of the poo advisers, stainless steel or plastic for a holding tank?
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:D
GRP definately. Make your own for next to nothing. See PBO442 Oct 2003 Practical projects.
It can be done easily like so. First make out of polysteyrene foam a plug of the proposed tank. Making sure you have a decent radius to all corners. Cover in parcel tape. Lay on the glass mat rich in resin. Add extra to the corners. When cured, cut down the middle so that you have two halves. Pull out the poly plug. If additional glass is to be added, then clean first with acitone and then lay on. Place the two haves together and glass the cut. Starting at four inches wide increasing to six. In order to put the fittings on, it is necessary to cut a hole or fit a floatation chamber inspection hatch. If you choose a hole, jig saw the section out, put in the fittings and the glass in the section the you cut out. Best fitted with aerosol foan. Easy too.
However, the PBO article covers it all inc photos.
Good luck and happy pooing.
 
I was fitting my Tek Tank yesterday. I think it is made of HDPE - the same stuff chopping boards are made from. In fact as a gimmick Tek Tanks put in the box of bits a chopping board with the boat name impressed in it. "here you are dear" Big smile. :):rolleyes:

Having a day off boat fixing to straigthen my back and knees - a few hours in a cockpit locker was not much fun.
 
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