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Holding tank replace/repair?!


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Hi all... my boat has a holding tank problem.. it’s 20 years old and it’s only just started so I can’t complain.. it needs sorting though! 

There is some corrosion and pitting and it’s leading to the odour escaping. 

It either needs replacing or welding. 

I imagine removing it would be a nightmare.. would need cutting up to fit through any gaps. PONG!! 

Could a new tank be built AROUND the existing one, or WITHIN? Leaving it in situ?! 

Anyone have any experience of this? Tips? 

Keen to learn ASAP! 

Jason. 

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I have seen a few like this.  Welding repair is probably pointless.  The whole tank top will be like lace and the sides at the top will be little better.  The bottom and lower sides may be better, or not,  depending on how well and how often the tank has been emptied.    Is it integral with the structure of the boat or does it have its own sides, top and bottom?  If it is integral you can expect the trouble to involve the parts shared with the hull.

Removal and replacement is unfortunately the only way forward.   An alligator saw is the weapon of choice rather than an angle grinder ( sparks go everywhere) though if you have access to a gas axe that might also be helpful but take care not to set the boat alight!   As you say, expect long and loud pong.  Now is a better time than summer! 

Start by giving it the best wash out you can.  Then  make a hole in the top and investigate whether there are any leaks from outside or bad hull corrosion (integral type tank) .  If so fix these first.  After that it is  just a question of one piece at a time.

I would want to replace with a plastic tank as they don't corrode.  They do need to be well baffled though which make them harder to empty.

N

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8 minutes ago, jasonlovesthegroove said:

 

 

9 minutes ago, jasonlovesthegroove said:

Thanks for that thorough reply! 

It has its own top sides and bottom. 

I was wondering about plastic.. still have the problem of getting it in though..

How do you mean baffles?

   No worries about the hull integrity then.

Baffles are vertical pieces ( with holes for liquids to pass through)  within the tank that stop the contents sloshing around when, say, you hit a lock gate or are in a turbulent lock. Too much sloshing can overload the tank top.  Baffles also serve to stiffen the tank top and sides enabling them to be thinner ( cheaper).

N

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No the hull is solid. Just this tank. 

I already covered a few thin looking areas with.. well it was stove sealant-as I’d just bought some for the stove and it’s obv solid stuff! And also epoxy on 2 small holes. Hasn’t cut the mustard though. So there are obviously other areas I can’t see. Leaves me thinking replacement might be the only way. There were crusty bubbled up areas and when rubbed down just left thin looking steel pitted areas. In 2 cases, a hole. 

Guess it’s become thin all over. Wonder how.. shame. Big job ahead it seems. No pun. 

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we have plastic ones on Tyto - they were fitted before we bought the boat. They are about 40gallons capacity and occupy space under the bunk beds. They seem to be working well. I don't think that they have baffles in them. There are manufacturers who advertise in the waterways press, it would be worth talking to a couple of them. It may only be necessary to cut the top off the existing tank, clean it out and then fit a plastic one inside it utilising the existing pipe connections.

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2 hours ago, Richard T said:

we have plastic ones on Tyto - they were fitted before we bought the boat. They are about 40gallons capacity and occupy space under the bunk beds. They seem to be working well. I don't think that they have baffles in them. There are manufacturers who advertise in the waterways press, it would be worth talking to a couple of them. It may only be necessary to cut the top off the existing tank, clean it out and then fit a plastic one inside it utilising the existing pipe connections.

A 40 gallon tank is quite small. You could easily get one of these in if it narrow in one dimension - and likely a bigger one. Check with the manufacturers.

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Hopefully this will focus your mind. The owner has had the boat from new (20 years), thought the steel tank under the bed was getting smelly this year.

We got it out.....just.

The owner had a pump out before we started...luckily.

 

New STAINLESS steel tank now installed.

 

20180321_140604.jpg

20180321_140611.jpg

20180321_140621.jpg

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9 hours ago, jasonlovesthegroove said:

Ooh dear.... that really needed doing! Surely the smell was there for a while!.? Mine isn’t that bad, but I’m def doing it now BEFORE it gets that bad! 

I’m planning to replace it with a plastic one though. Can anyone suggest why I shouldn’t?

 

thanks for the pics. 

No. Go for it.

Edited by Dr Bob
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25 minutes ago, J R ALSOP said:

That just about sums up holding tanks.

I beg to differ. Polyethylene tanks of sufficient thickness and quality are excellent for the duty. The bees knees! (Rusty.....NO).

Edited by Dr Bob
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