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Weight of holding tank ?


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Our mild steel holding tank has sprung a leak,  so we need to get it out.

I have been trying to calculate how heavy it would be if empty, but I dont know how thick the steel is. Does anyone know what gauge steel these were usually made of?

I guessed at 2mm which gives me a weight of about 40 kilos. I was hoping it would be lighter as lifting that out is going to be a problem !

 

Thanks

Steve

 

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8 minutes ago, David Mack said:

Are the dimensions of the tank such that you can get it out through a doorway?  If not you will have to cut it up inside the boat. But at least the pieces will be lighter.

Yes, it will be a bit awkward but it should fit out through the rear doors and slide.

 

44 minutes ago, Onewheeler said:

The one I cut up recently on our mainland boat was 3mm steel.

 

Martin/

 

ps I've got a leesan polyethylene tank taken out of the uk boat looking for a good home

Hi Martin

That's not what I wanted to hear! At 3mm that makes ours about 60 kilo.

We wont be able to lift that out. So I may have to think about cutting it up.

Was yours a particularly messy job ?

 

Steve

 

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4 hours ago, Just Heaven said:

Yes, it will be a bit awkward but it should fit out through the rear doors and slide.

 

Hi Martin

That's not what I wanted to hear! At 3mm that makes ours about 60 kilo.

We wont be able to lift that out. So I may have to think about cutting it up.

Was yours a particularly messy job ?

 

Steve

 

The tank hadn't been used for some years and I like to think that the stuff in the bottom was dry rust. If I'd removed that thoroughly it wouldn't have been too bad for mess.

 

I reckon that tank was about 85 kg and was in any case too big to go through the engine room hatch. It took about 6 m of linear cut to get it into manhandleable chunks to pass up to the missus. A combination of reciprocating saw and jigsaw did the business, both needed as only one or the other could access some areas.

 

Took about 3 or 4 hours work. A lot of dust from the rust or whatever but not too bad for metal swarf or filings.

 

If anyone wants my leesan tank it's 40 cm h x 60 x 90.

 

Martin/

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5 hours ago, billS said:

This thread just shows why mild steel holing tanks are a bad idea. I have seen a 6mm mild steel tank perforate within 15 years.

 ... a serendipitous typo :D :cheers:

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9 hours ago, Detling said:

Make sure it is not part of the structural strength of the boat or a bulkhead and definitely not sure or bottom. 

No, it's definitely a completely separate, self contained tank.

 

Steve

 

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  • 4 weeks later...
On 26/07/2018 at 12:42, Onewheeler said:

The one I cut up recently on our mainland boat was 3mm steel.

 

Martin/

 

ps I've got a leesan polyethylene tank taken out of the uk boat looking for a good home

The job has now been done, see here http://www.justheaven.org.uk/2018/08/new-holding-tank/

 

Many thanks to Onewheeler Martin for suggesting the reciprocating saw. 

 

Steve

 

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We have, for months, been considering removing our holding tank. Unless I take the bed apart I cant ascertain whether the tank is integral to the base plate. (Base plate is base of tank). Of course I can take the bed apart, but knowing me,as I do, I'll go so far and not be able to stop and have the whole area in a right state. I'm one of those chappies that need to have a plan of action, and have no idea what I'm letting myself into. 

So, may I ask?

Nightwatch is an early 1990s boat. Is it likely that the above practice was still in use or was it down to individual boat builders to decide. The hull was manufactured by Dave Clarke. (Before anybody asks, it was after his pop stardom). Was it their practice to build integral tanks. I hope not.

 

(Some years ago a chap came on here to announce that he fitted out Nightwatch and knew all about the boat. He worked at Bromsgrove Boats who fitted out the boat. Haven't heard anything from him since. I had so many questions for him as well.  I'd like to get in touch. Anyone know of him).

 

 

1 hour ago, Just Heaven said:

The job has now been done, see here http://www.justheaven.org.uk/2018/08/new-holding-tank/

 

Many thanks to Onewheeler Martin for suggesting the reciprocating saw. 

 

Steve

 

I will view your blog to gain experience. Thank you.

Edited by Nightwatch
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45 minutes ago, Nightwatch said:

We have, for months, been considering removing our holding tank. Unless I take the bed apart I cant ascertain whether the tank is integral to the base plate. (Base plate is base of tank). Of course I can take the bed apart, but knowing me,as I do, I'll go so far and not be able to stop and have the whole area in a right state. I'm one of those chappies that need to have a plan of action, and have no idea what I'm letting myself into. 

So, may I ask?

Nightwatch is an early 1990s boat. Is it likely that the above practice was still in use or was it down to individual boat builders to decide. The hull was manufactured by Dave Clarke. (Before anybody asks, it was after his pop stardom). Was it their practice to build integral tanks. I hope not.

 

(Some years ago a chap came on here to announce that he fitted out Nightwatch and knew all about the boat. He worked at Bromsgrove Boats who fitted out the boat. Haven't heard anything from him since. I had so many questions for him as well.  I'd like to get in touch. Anyone know of him).

 

 

I will view your blog to gain experience. Thank you.

Can you see the bottom of the tank without destroying stuff? If it's a separate tank you will be able to tell if you can get to the bottom and see if it's either laid on steel bearers or indeed on to decking.

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8 minutes ago, mrsmelly said:

Can you see the bottom of the tank without destroying stuff? If it's a separate tank you will be able to tell if you can get to the bottom and see if it's either laid on steel bearers or indeed on to decking.

 

Or can you drop a dipstick down the loo to the bottom of the tank to judge whether it is as far down as the bottom plate?

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3 hours ago, David Mack said:

 

Or can you drop a dipstick down the loo to the bottom of the tank to judge whether it is as far down as the bottom plate?

Not if its a macerator bog? The last one I removed was luckily a stainless steel tank laid directly onto the deck but was still a heavy thing to lift out.

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On ‎26‎/‎07‎/‎2018 at 15:17, billS said:

This thread just shows why mild steel holing tanks are a bad idea. I have seen a 6mm mild steel tank perforate within 15 years.

That's just what I didn't want to read.:closedeyes: Mine's 6 mm and been in use for about 15 years. It's the one thing I dread. At the time I wanted the builder to install a S/S one but he convinced me otherwise. Out of curiosity where did it fail? 

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5 hours ago, Slim said:

That's just what I didn't want to read.:closedeyes: Mine's 6 mm and been in use for about 15 years. It's the one thing I dread. At the time I wanted the builder to install a S/S one but he convinced me otherwise. Out of curiosity where did it fail? 

Surprisingly ours went at the top. It was fairly thin in several places, but the only actual hole was along one edge on the top.

It's difficult to know how thick it was originally but I'd guess about 4mm. It was 14 years old.

 

Steve

 

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16 hours ago, Slim said:

That's just what I didn't want to read.:closedeyes: Mine's 6 mm and been in use for about 15 years. It's the one thing I dread. At the time I wanted the builder to install a S/S one but he convinced me otherwise. Out of curiosity where did it fail? 

Yeah but.... the baseplate is probably 10mm so providing you're not losing baseplate from the outside at a similar rate to whatever degradation is going on inside the tank, any leak really ought to be inside the boat and therefore will be detectable long before anything catastrophic happens to the watertight integrity of the hull.  My guess is that most tanks in reasonably built boats aren't failing at 15 years.  Would those who do this sort of repair work say that those which do fail do so by weeping internally, probably around top of the tank? 

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16 hours ago, David Mack said:

Is there some accessible fitting on top of the tank which can be disconnected to allow the dipstick test?

Some do some don't. This boats tank is easy to get out and fitted onto deck boards. This tank is made out of plastic so at least it's easy to cut up if I need to take it out.

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I know of one boat, Drum Solo, where I was told that the baseplate was the tank bottom and it did perforate. But I don't know how thick the baseplate was.

I drilled mine for a level switch and it was still 6mm. Most that I have seen failed or removed have rusted mostly on the top. I suspect that the part below gunge level is fairly well pickled, the top gets wet and dry and is in air most or all of the time.

Bet there is not much oxygen at the bottom and methane is at the top.

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