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Water Tank bangs

Supertramp
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Supertramp Contributor

Supertramp

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My stainless steel water tank in the bow makes a loud bang and quiet substantial vibrations through the boat when filling, (and emptying..)

I haven't been worried by this, as when i got the boat a year ago, someone told me it was quite normal, - its only when nearly full and im guessing its the top plate flexing.

 

However, a recent thread about building boats out of stainless steel said that the welds were weaker in stainless steel.

Should I be worried that constant flexing during use will weaken the welds? I live-aboard, so it is used alot.

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Grace and Favour Veteran II

Grace and Favour

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Posted (edited)

My stainless steel water tank in the bow makes a loud bang and quiet substantial vibrations through the boat when filling, (and emptying..)

I haven't been worried by this, as when i got the boat a year ago, someone told me it was quite normal, - its only when nearly full and im guessing its the top plate flexing.

 

However, a recent thread about building boats out of stainless steel said that the welds were weaker in stainless steel.

Should I be worried that constant flexing during use will weaken the welds? I live-aboard, so it is used alot.

 

Would I be right in thinking that the tank 'bangs' just a few minutes before it's full?

 

(OOOps! - just noticed that's what you have described! )

 

Well, ours does the same - and I've worked out it's because the air-vent pipe is fotted in the wrong point of the tank - the 'bang' is the air forcing its way out and thus causing the flexing.

 

 

Our tanks does exactly the same . . . and we make a point of stopping the fill just before that point

Edited by Grace & Favour
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Supertramp Contributor

Supertramp

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Would I be right in thinking that the tank 'bangs' just a few minutes before it's full?

 

Thats right G&F, I understand whats happening as far as water pressure, but it is concerning me that welds on steels shouldn't have to cope with these stresses, and may actually fail?

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Tony Brooks Veteran II

Tony BrooksDonate to Canal World

Posted
Posted

My stainless steel water tank in the bow makes a loud bang and quiet substantial vibrations through the boat when filling, (and emptying..)

I haven't been worried by this, as when i got the boat a year ago, someone told me it was quite normal, - its only when nearly full and im guessing its the top plate flexing.

 

However, a recent thread about building boats out of stainless steel said that the welds were weaker in stainless steel.

Should I be worried that constant flexing during use will weaken the welds? I live-aboard, so it is used alot.

 

 

I agree its probably the top plate but the question is why? I suspect it is a bit like those spring "clickers" we used to get on the back of a tin frog when young in that it has natural bow with the strain in the plate tending to hold it in place. When sufficient internal pressure (or lack of pressure) builds up the box flips back the other way.

 

I also agree it would be best to try to stop it. First make sure the tank breather system is not bocked (some low down breather holes have been known to be blocked with mud from the bank).

 

Then if it is clear and if it was my boat I would be squirting some foam into the gap between the well-deck sole and the top of the tank in the hope it would hold the "bow" down all the time.

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Guest

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We have had hire boats that did this - we were always told it was normal and a good indication the tank was nearly full. I believe these had stainless tanks that were not integral to the hull.

 

Our own boat which has an integral tank does not do it.

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Guest

Guest

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I bet you're relieved about that!!!! :rolleyes:

 

It was when we first got the boat that I fully realised the difference between the two different types of tanks - filling our own for the first time and waiting for the 'bang' that never came.....

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allybsc Rising Star

allybsc

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My stainless steel water tank in the bow makes a loud bang and quiet substantial vibrations through the boat when filling, (and emptying..)

I haven't been worried by this, as when i got the boat a year ago, someone told me it was quite normal, - its only when nearly full and im guessing its the top plate flexing.

 

However, a recent thread about building boats out of stainless steel said that the welds were weaker in stainless steel.

Should I be worried that constant flexing during use will weaken the welds? I live-aboard, so it is used alot.

 

 

Our tank does this too, never worried us. When we hear the first bang we go out to turn the tap off.

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allybsc Rising Star

allybsc

Posted
Posted

My stainless steel water tank in the bow makes a loud bang and quiet substantial vibrations through the boat when filling, (and emptying..)

I haven't been worried by this, as when i got the boat a year ago, someone told me it was quite normal, - its only when nearly full and im guessing its the top plate flexing.

 

However, a recent thread about building boats out of stainless steel said that the welds were weaker in stainless steel.

Should I be worried that constant flexing during use will weaken the welds? I live-aboard, so it is used alot.

 

The engineer sat to me on the sofa tells me that a steel tank needs a bit of flex to cope with changes of temperature.

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johnmck Rising Star

johnmck

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We have had hire boats that did this - we were always told it was normal and a good indication the tank was nearly full. I believe these had stainless tanks that were not integral to the hull.

 

Our own boat which has an integral tank does not do it.

 

 

Ours is stainless and does this. I would be bloody worried if an integral tank made a similar noise ! :cheers:

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davel Contributor

davel

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The s/s tank on Iona used to bang when filling. When we had our first week on board moving nearer to where we lived we assumed that having to take on a lot of water was because we were doing a lot of cleaning. When we were about to leave her I thought I would just check under the floor and found water just about touching the underneath of the floor. The tank was leaking but because I could not get round it to find the leak I cut it out built a bulkhead and had a flexible liner made to fit right in the front of the bow (gaining a lot of extra storage space). I never did locate the leak but assumed it was metal fatigue from the flexing.

 

Edit to add the boat and presumeably the tank was 20 years old.

Edited by davel
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Darren72 Rising Star

Darren72

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Thanks for all the replies, good to know its a common experience, - all be it still a little disconcerting, but if I can get 20 years out of it - it will see me out.

We hired a boat once which banged all the time when we used water, regardless to been full or empty. It sound like someone hammering the tank from the inside. After a few days we found a damp patch on the floor which got worse and worse. I realised they had put a diesel cap on the water tank filler. No pressure release in it. The tank had a leak, we got a weeks holiday for free and free fuel.

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Matthew Dowson Community Regular

Matthew Dowson

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Ours doesn't bang but it did flex due to a blocked airhole and one stainless steel weld at the top has given way, it has been filled with coldweld but will leak a little if I dont pay attention when its full. So yes, stainless steel welds can give if there is a problem with venting.

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system 4-50 Veteran II

system 4-50Donate to Canal World

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Depends on how fast you are filling it and drawing teaer off. I am sure 1/2" id would be fine and suspect some vents are just a 3mm hole in the filler cap.

Thanks TB. I need to install one of these in the next couple of weeks & I wasn't sure what size to go for. 1/2" it is then.

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