bavaria 47 2001 need new water tanks at bow

[xmax]

Dear All Happy new year

I have leaking problem at my two forward water tanks
this tanks serve very well for a decade and more but now they had crack on top and during filling start leaking

i want to find what alternatives i have to replace tanks, to bond, to privide some special filling method with floater so to avoid tank pressurization, keeping the high level lower from the top?
i try bonding but with poor results best solution to buy new ones. construction from S.S is possible but i don't like.
from the suppliers of bavaria or other
the measurements of this tanks are stbd tank 130x80x42 and port tank 130x57x45 triangle with conical shape they are marked with some letters as w180 propably this is the type of the tank

waiting to hear how others handle this problem

[Salty]

Hi Xmax, thanks for your good wishes.
I don't think having a filling restriction with floating device will provide either value for money, or peace of mind. The difference in head height of water between the top of the tank and the filler cap will make very little difference in regard to the pressure on the sides or top of the tank. Your problem I think is that your boat most likely had a tank with faulty construction which combined with rapid movement of water, or sloshing within the tank while it was only partially filled, most likely caused the damage. Keep in mind that one atmosphere pressure will support a column of water some 32 feet in height, so the head height of your filler cap would make a difference in pressure of little more than a puff of wind. On the other hand, slamming into a heavy sea will cause the contents of the tank to accelerate forwards and upwards at high speed against the top of the tank, and that will give you more grief than the very slight increase in tank pressure caused by filling to a level within the height of the filling line. In such weather conditions you would most likely be better off filling the tank until it overflows, and not using any water from it until the weather had improved.
However, the foregoing does assume that you only fill using an ordinary hose poked into the filling connection, and not by some method involving coupling the filling hose to a permanently fitted connection that would not allow any excess water to simply overflow. In such instance the hydraulic effect would overcome the strength of the tank in no time at all.

[Nigel]

I would look at some plastic welding devices, cheaper than a new tank and useful to have.

[Spirit of Mary]

The tanks are normally made of PE. You can't glue this material, but it is good weldable. You need PE weld material and a hot air source which can be directed to a narrow spot, for melting the weld material and tank material.
I was thinking that my aft cabin tank was leaking and needed to be replaced. So I saw a bigger cover hole out in my aft cabin bed bottom. By doing this I also cut the tank. Afterwards the tank didn't leak, but the boiler. I repaired the cut in the tank by hot air welding without any problem/leak so far (6 years).
Ger

[wellsy]

G'day Max  , had similar water tank problem with my 2000  42'  bow tank had very small Crack at front of tank on top  near moulded curve . Could not figure where or why it leaked.one day with hose in empty tank and front hatch open and bed base up I started filling . Here's what happened as tank approached almost completely full it made a popping sound and actually changed shape (flexing) .in short tank was not firmly held by expanding foam used to anchor tank into bow of boat.I purchased  aerosol can of expanding foam and re sealed between tank and hull (tank must be full when resealing)  used a 2 part adhesive / SEALER  Wurth I think it was called  been dry for over a year now  and  subjected to some heavy going   I reckon  small Crack only happened  as a result of flexing .good luck hope this helps  Wellsy

[Cassiopeia]

This is way after this thread was last posted to, but I thought I'd add some thoughts that can turn up in someone's search.

We have a 1997 Bavaria 46E. There are 2 200L tanks under the front berth. One of them developed a crack in the top corner edge near the inspection port. I purchased a plastic welding tool (basically a solder iron with a special tip) that came with some LDPE material. I tried to seal the crack using this tool and this material, but was still getting small leaks.

In contacted the tank manufacturer (Cipax.com in Sweden) whom I've dealt with before (they sent us new tank lid covers and seals!!!) about the kind of plastic used. These tanks are MDPE. Laundry detergent bottles are #2 recycle code = MDPE.

We scrounged an empty laundry detergent bottle and I cut strips. I then used my heat gun, and found that the heat gun with the strips of material worked MUCH better and were easier to manage to lay down strips of material that sealed.

Be sure to prep the surface first: use a small wire brush, and clean it.

[Salty]

Very useful information Doug, especially the tip about the laundry bottle, thankyou.

[UP]

I'm adding to this discussion to benefit future forum searches: I have a bavaria 47 Cruiser 2001 with a very similar stress crack at the top left corner of the slosh/compression baffle, forward left water tank. This summer I took a Dremel and ground out a v groove of the crack, used a milling bit, and tried welding it with LDPE and HDPE (I did not have MDPE rod available) and this did not work. Surfaces were very well prepared. The adhiesion was not 100% and the crack still leaked (see images below, one of the pictures is taken from inside the tank). While in theory HDPE should weld to MDPE (?), not in this case. I'm looking for MDPE rod now to redo the job. To my understanding, welding rod color should not matter. I'm not excluding the option that my welding rods might have contained some moisture. Probably the best result in welding will be achieved when the rods are dried in ~50 C for some hours before welding. I know from 3D printing of plastics that filament moisture content can wreak havoc on print quality. Same goes for the weldable surface.

In summary, my recommendation for plastic welding this crack:
1) Use MDPE for welding, not LDPE or HDPE;
2) Dry your welding rod/material for 2 hours at 50 C, oven, apply heat with an electric fan or whatnot to the crack;
3) Surface preparation is paramount, clean the crack with solvents, brush it up, V-groove it with a knife blade/Dremel.