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Blackacre · 05-11-2018, 14:17

My aft water tank has a leak coming from a hairline crack on the bottom. The previous owner tried to patch it with no avail. Curious what others would do in this situation.

1. Replace the tank? - It hasn't been easy finding a replacement and shipping to the Caribbean may make this option impractical. L'Oceane des Plastics 200L

2. Repair the tank? - This has been tried twice already. The crack is under a lot of pressure when full. Maybe plastic welding but I have never done plastic before and can't find anyone with experience near me.

3. Operate exclusively from the forward water tank and install a water maker where the aft tank used to occupy.

- Beneteau Oceanis 46

J.Kitchens · 05-11-2018, 14:35

You could find someone to weld a stainless tank for you.

OR

Insert a bladder into the damaged tank to reclaim some of the water storage space.

If either of my tanks started leaking I'd put a bladder in it until I could find someone to make me a stainless tank.

thinwater · 05-11-2018, 14:52

Detailed in the December issue of Practical Sailor.

Welding is tricky and maybe impossible through an access hole. You would have to practice on something else.
G-Flex or Sika 291 can be very effective if reinforced properly. I've done this on fish pond liners (same material) and had the repairs last >15 years. Surface prep is VITAL; sanding + heat treatment. Yes, Sika 291 is food-rated and immersion rated.

NOT regular epoxy. It will pop right off. Not repair kits from the autoparts store; they are NOT for LDPE (what the "4" indicates).

**GordMay** · 06-11-2018, 06:07

TIPS FOR WELDING THERMOPLASTICS ➥ TIPS FOR WELDING THERMOPLASTICS | King Plastic Corporation

Terra Nova · 06-11-2018, 07:04

Quote:

Originally Posted by Blackacre

...It hasn't been easy...
can't find anyone with experience near me...

If you believe you can't, you're right.

"It's too hard" is what prevents most people from achieving their goals.

Zai · 06-11-2018, 08:15

If you can get the tank out, I would weld it.
I had a big crack in my blackwater tank and I cleaned it up and welded it myself. I didn't have any experience welding plastic, but it went just fine.

I pressure tested it after and it holds very good.

Used a hot air gun.

Captain Puget · 06-11-2018, 08:49

+1 for the bladder.

The access hole you cut to install the bladder becomes the inspection port and the tank provides the bladder support. You may want to consider rash-guard/ liner bag to prevent bladder wear due to sea motion.

MJH · 06-11-2018, 09:52

You haven't given us much useful information.

How bad is the leak...ounces, pints, quarts per hour or day?
How big a tank, gallons and dimensions?
Where is the tank located?
What material is it made of?
What access do you have to the leak itself, both inside and outside?
Can the tank be removed from the boat without surrounding damage?
What make/model/year of boat?

A useful remedy will depend on all these answers.

~ ~ _/) ~ ~ MJH

Blackacre · 06-11-2018, 10:04

Is the bladder a temporary fix? I do have an access panel on the top of the tank. Enough to get your hand inside. The crack is on the bottom so any sanding/prep/welding would likely need a new access panel. Can one be added to the side or bottom or under the water line. I suppose with a bladder it wouldn’t matter but what if I just welded the tank?

- the tank is easily removed from the boat

Blackacre · 06-11-2018, 10:11

Quote:

Originally Posted by MJH

You haven't given us much useful information.

How bad is the leak...ounces, pints, quarts per hour or day?
A: 10G per day,
How big a tank, gallons and dimensions?
A: odd shape. 52gal
Where is the tank located?
A: Aft, under the berth.
What material is it made of?
A: plastic
What access do you have to the leak itself, both inside and outside?
A; top access panel. Can only see hairline crack.
Can the tank be removed from the boat without surrounding damage?
A: yes. No issues removing the tank
What make/model/year of boat?
2007 Beneteau 46

A useful remedy will depend on all these answers.

~ ~ _/) ~ ~ MJH

See comments above

Zai · 06-11-2018, 10:25

It's a no-brainer.

Take it out and weld it.

Plenty of help with you tube search welding HDPP.

Peregrine1983 · 06-11-2018, 10:26

Quote:

Originally Posted by Blackacre

See comments above

I'll bet these guys will make you a tank and ship it to the Caribbean. I just had them do a new waste tank for my boat and they shipped it across the US. Cost me $270 plus like $90 for shipping.

RONCO PLASTICS
https://ronco-plastics.com/product/w...-holding-tank/

I picked the size and shape from the list of tanks on their site and emailed a picture showing them where I wanted the inlet and outlets located.

Tank is perfect. Took only a week or two.

MJH · 06-11-2018, 11:11

Thanks for the details.

I would first go to the boat manufacturer, Beneteau, and see if they had a replacement, a referral to the tank vendor, or another manufacturing source.

Baring that I would remove the tank and "thoroughly" dry it out as any repair/replacement will start with that action. You can now get the full tank exterior dimensions and seek someone to make a new one if desired.

My knowledge of plastics is limited but you need to make sure any repair/replacement is made with material that is not toxic to the contents.

With that in mind you might tape the bottom of the tank crack to prevent the exit of repair material and then pour enough repair material into the tank to cover the bottom of the tank sealing the crack. This will minimize the loss of tank volume and the broad coverage will help support the internal tank pressure on the cracked area.

I would not jump to getting a water maker...viewed as the most expensive alternative.

Good Luck.

~ ~ _/) ~ ~ MJH