Princess Owners Club

ebonita · Joined: 03 Jul 2007 Posts: 10 Location: Sweden

My Princess 40 is equipped with aluminum tanks for fuel, water and toilet holding. Especially holding tank made of aluminum sounds high risk! So at any the slightest sign of odour I look at the aluminum holding tank and the possibility to change it to plastic....

Anyone having experiences on this topic?

markdj · Posted: Fri Sep 21, 2007 8:46 pm Post subject:

The tanks are marine grade aluminium though I would have thought that the fuel tank is steel as ours is.

Regarding holding tanks, I don't see why it should be a problem. All holding tanks have a breather like a fuel tank so that is where you would expect your whiffynes to comes from. Also, check that pipes are ok, wipe with a damp cloth, if the cloth smells then it's time to change the pipe. Not sure if you can or not but maybe using a treatment in the holding tank might help?

ebonita · Joined: 03 Jul 2007 Posts: 10 Location: Sweden

markdj wrote:

The tanks are marine grade aluminium though I would have thought that the fuel tank is steel as ours is.

Regarding holding tanks, I don't see why it should be a problem. All holding tanks have a breather like a fuel tank so that is where you would expect your whiffynes to comes from. Also, check that pipes are ok, wipe with a damp cloth, if the cloth smells then it's time to change the pipe. Not sure if you can or not but maybe using a treatment in the holding tank might help?

Hello Mark, and thank you for your reply.

Reason for my question is 1) some odour in my boat and 2) a number of testimony's on the Norwegian Baatplassen.no which is a very active forum with numerous very competent writers (unfortunately not so many regarding Princess boats). The predominant opinion there is that Aluminum holding tanks are bound to leak within not to many years, and they refer not Princess, but to several other well known shipbuilders with frequent problems. Also the English writer Peggie Hall who appears to know something on this subject writes: "Although you'll see aluminum and stainless holding tanks, no metal of any kind should ever be used to hold sewage.
Urine is the most corrosive material it's possible to put next to any metal. If you doubt me, gentlemen (ladies will have to take your word for it), notice the dividers between urinal stalls in men's rooms. If that facility has been open for more than a week, no matter how clean and well-maintained it is, even though the dividers are stainless steel coated with enamel you'll see rust stains from the bolts that attach the dividers to the tile. While the walls of a metal holding tank may last a decade or more, the welds will typically begin to leak at a seam or a fitting in two
to five years, and the tank will have to come out for repair or replacement."

But as said above, so far I have found no statement on problems with holding tanks in Princess boats. So I hope you are right and that Marine Projects know what they are doing - as they obviously do on most things they conduct...
Your boat is some years older than mine, and I understand that you have no problem in this respect.

markdj · Posted: Sat Sep 22, 2007 4:28 pm Post subject:

If you cna get access to the tank, then have a look around it and in the bilge, otherwise just check for sweating pipes and the breather. Most likely it is the breather that is giving the smell. Of course, it could also be the heads themselves or the pump - maybe the seals are leaking.

We don't have holding tanks but I do notice that all the new boats can be fitted with plastic holding tanks, only using aluminium for fuel and water.

Reading here,

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is where that info came from.
Regarding the afore mentioned toilet blocks, they use 304 stainless which will rust very quickly anyway, even in the rain outside.

Best thing is to examine the tank closely, using a mirror and light to get all round it, then you can see if the tank is the problem or not.

ebonita · Joined: 03 Jul 2007 Posts: 10 Location: Sweden

Dear Mark,

Regarding inspection of the tank, yes I can see the top of the tank, the rest is enclosed in a inaccessible spacing. But there is no noticeable leakage from hoses or down to the bilge. However from the Norwegian sources there is more talk about porous parts in welded areas with crystalline signs outside the tank.

The heads I exchanged 2005 to Telfa silent running with centrifugal pump. A great improvement from the former heads with impellerpumps! When exchanging the heads I fond that one of the hoses was full with urine stone, so some of the more accessible hoses were exchanged at the same time. This year I replaced the hand operated holding tank empty pump with a Telfa electric diaphragmatic pump which is more silent and more tolerant to debris and dryrunning compared to the standard electric centrifugal pump. So I put a 10 minute timer relais to run the pump which empties the tank and helps not to forget it on.

Me too have read the Tek-tanks home page and also they /of course/ talk them self warm for plastic tanks. So.... maybe some day I will take the jigsaw or angle grinder and cut the present tank in pieces and replace with plastic.... Awful jobb....

_________________
Princess 40 year 1999
2 x Volvo TAMD63P

rolferikmartinsen · Joined: 29 May 2006 Posts: 4 Location: Asker, Norway

The weakest point in a metal holding tank will always be the welding seems. Foreign, impure material is added during the welding process, causing corrosion, stress and finally cracks. In addition, in aluminum tanks you will sooner or later face a phenomena called pitting, forming so called pit holes.
Some aluminum alloys are better than others of cause. Seawater resistant aluminum in the Al57S series or equivalent is among the better ones.