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moiuk

Water tank empty too soon

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The vent on my water tank is identical to the one on my diesel tank; the builder said that the advantage of the flame arrested gauze is that it ensures no insects can get in. However a disadvantage is that on anything fast like the hose at a Thames lock, the air cannot escape quickly enough when filling so that it appears to be full (ie the inlet overflows) when it is actually less than half full. Could this be the OP's problem?

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4 minutes ago, system 4-50 said:

Try unscrewing the vent and dipping the tank when you think it is empty?

yes I will do this. Seems like the most likely issue. The vent must be blocked or otherwise not working if this works.

1 minute ago, Keeping Up said:

The vent on my water tank is identical to the one on my diesel tank; the builder said that the advantage of the flame arrested gauze is that it ensures no insects can get in. However a disadvantage is that on anything fast like the hose at a Thames lock, the air cannot escape quickly enough when filling so that it appears to be full (ie the inlet overflows) when it is actually less than half full. Could this be the OP's problem?

when it is full, the water level stays at the top level with the cap. I would assume e that it would still go down (slowly)  if this was the case?

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3 minutes ago, moiuk said:

yes I will do this. Seems like the most likely issue. The vent must be blocked or otherwise not working if this works.

I meant using the vent to determine whether there was water in there or not. I know nothing about blocked vents.

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13 minutes ago, Detling said:

Seconded looks several years of grime there, plus the sealant round that vent is dreadful. Have you paid him?

 

the sealant there is very bad, and almost certainly not original. There must be a reason why the vent was replaced, and possibly put so much sealant in that it has blocked the vent altogether? 

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I would suggest when the tank is really empty you move that level transducer to the otherside of the isolation valve and screw the valve straightight into the tank.

 

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Just now, system 4-50 said:

I meant using the vent to determine whether there was water in there or not. I know nothing about blocked vents.

Ah yes. I will find something clean that I can dip in to check the water level.  I hesitated, because I didn't want to dip a stick or otherwise that would contaminate my water... couldn't think of something thin and long that would be clean..

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Surely there is decent access to the tank, if only for periodic cleaning. There's a whacking great hatch on my front deck - I have to get right inside the tank to clean and repaint it.

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Just now, moiuk said:

Ah yes. I will find something clean that I can dip in to check the water level.  I hesitated, because I didn't want to dip a stick or otherwise that would contaminate my water... couldn't think of something thin and long that would be clean..

A tape measure

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2 minutes ago, ditchcrawler said:

I would suggest when the tank is really empty you move that level transducer to the otherside of the isolation valve and screw the valve straightight into the tank.

 

Good idea. The isolation should be the first thing.

1 minute ago, ditchcrawler said:

A tape measure

smart thinking. Thanks.

2 minutes ago, Arthur Marshall said:

Surely there is decent access to the tank, if only for periodic cleaning. There's a whacking great hatch on my front deck - I have to get right inside the tank to clean and repaint it.

its sealed under the front deck. Access is from under the steps out to the deck (as per my previous photo). Filler point and breather are through the deck directly into the tank.  Seems to be completely integrated with the initial build.

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so, can confirm tank is definitely full now, so no issues with not filling fully.

 

One thing that is strange to me, which I've not mentioned before, is that when I thought the tank was empty, I got some dirt through the taps, which seemed strange. Looking into the tank through the fillee, the bottom of the tank looks clean so I am not sure where the dirt came from, especially as it looks like the tank was 2/3rds full when it ran dry.

 

The filter looks a bit dirty, but nothing more than I woukd have expected..

20200801_222936_exported_985038549453792374.jpg

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One problem I have is that the draw off pipe gets clogged with, probably, rust. Then the pump pulls air in, I get a mixture of air and water. It's never pulled no water at all through though. Those filters can be a problem too. They can block and suck air in. Try it without it.

As it seems you can look down and see into the tank, if it runs dry too quick again, check the water level is still above the draw point. If it is, the problem must be somewhere else! I'd start by taking the inlet pipe off the pump and see if water from the tank pours out, which it should if its all below the surface. If it does  then shove it back on the pump, take the other pipe off and run the pump. If no water comes out, it's the pump. If water comes out of the pump, shove the hose back on. If it still doesn't come out the tap, it's going somewhere else.

Mind you, you've probably thought of all that already.

Edited by Arthur Marshall

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1 minute ago, Arthur Marshall said:

Mind you, you've probably thought of all that already.

:D

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5 minutes ago, Arthur Marshall said:

One problem I have is that the draw off pipe gets clogged with, probably, rust. Then the pump pulls air in, I get a mixture of air and water. It's never pulled no water at all through though. Those filters can be a problem too. They can block and suck air in. Try it without it.

As it seems you can look down and see into the tank, if it runs dry too quick again, check the water level is still above the draw point. If it is, the problem must be somewhere else! I'd start by taking the inlet pipe off the pump and see if water from the tank pours out, which it should if its all below the surface. If it does  then shove it back on the pump, take the other pipe off and run the pump. If no water comes out, it's the pump. If water comes out of the pump, shove the hose back on. If it still doesn't come out the tap, it's going somewhere else.

Mind you, you've probably thought of all that already.

Certainly lots of tings for me to try next time it runs out of water too early next time.   It was a mixture of air and water when it ran out, so that water filter could also be the culprit. Can't see how it draws in air though?   Looking down in the tank looks clean, so would not expect rust to be an issue.

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7 minutes ago, Arthur Marshall said:

One problem I have is that the draw off pipe gets clogged with, probably, rust. Then the pump pulls air in, I get a mixture of air and water. It's never pulled no water at all through though. Those filters can be a problem too. They can block and suck air in. Try it without it.

As it seems you can look down and see into the tank, if it runs dry too quick again, check the water level is still above the draw point. If it is, the problem must be somewhere else! I'd start by taking the inlet pipe off the pump and see if water from the tank pours out, which it should if its all below the surface. If it does  then shove it back on the pump, take the other pipe off and run the pump. If no water comes out, it's the pump. If water comes out of the pump, shove the hose back on. If it still doesn't come out the tap, it's going somewhere else.

Mind you, you've probably thought of all that already.

Well there are 12 push fit fittings between the tank and the pump to leak air a 4 right angle elbows to block. The filters are known to suck air it the inlet gets blocked. Have you had it to bits, it looks like a few drips around there

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That filter is Very clean.

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7 hours ago, system 4-50 said:

Try unscrewing the vent and dipping the tank when you think it is empty?

 

Or just unscrewing the filler cap and doing the same thing? Try running a tap with the filler cap unscrewed in case that vent is blocked and there's a vacuum formed in the tank as it empties as someone else said.

7 hours ago, Arthur Marshall said:

Surely there is decent access to the tank, if only for periodic cleaning. There's a whacking great hatch on my front deck - I have to get right inside the tank to clean and repaint it.

 

You've got an integral tank, sounds like the OP has a stainless tank. They don't need repainting.

  • Greenie 1

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7 hours ago, moiuk said:

 

its sealed under the front deck. Access is from under the steps out to the deck (as per my previous photo). Filler point and breather are through the deck directly into the tank.  Seems to be completely integrated with the initial build.

 

I thought you said you'd measured it and it was an oblong 2 x 1 x 0.5m? That doesn't sound like an integral tank because it's not bow shaped. An integral bow tank is just an area formed by a bulkhead at the front of the boat. It is part of the boat rather than a separate tank.

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10 hours ago, moiuk said:

yes I will do this. Seems like the most likely issue. The vent must be blocked or otherwise not working if this works.

when it is full, the water level stays at the top level with the cap. I would assume e that it would still go down (slowly)  if this was the case?

Where is the breather relative to the filler, higher or lower? If lower I would expect the level to drop as water drains out the breather. Elsewhere you have said that you're reluctant to use a dip stick for fear of dirt. Wait until you take the inspection hatch off (assuming you have one) I suspect you will be surprised. I always use water containers for my drinking water. You can pick up a waterproof endoscope with light fairly cheaply on ebay. Poke that down and have a look. Going back to the inspection hatch if you have one . I would remove that now and have a look. Nothing like the MK 1 eyeball.

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3 hours ago, blackrose said:

 

I thought you said you'd measured it and it was an oblong 2 x 1 x 0.5m? That doesn't sound like an integral tank because it's not bow shaped. An integral bow tank is just an area formed by a bulkhead at the front of the boat. It is part of the boat rather than a separate tank.

Its stainless steel, but integrated into the bow so I have only limited access.

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1 minute ago, Slim said:

Where is the breather relative to the filler, higher or lower? If lower I would expect the level to drop as water drains out the breather. Elsewhere you have said that you're reluctant to use a dip stick for fear of dirt. Wait until you take the inspection hatch off (assuming you have one) I suspect you will be surprised. I always use water containers for my drinking water. You can pick up a waterproof endoscope with light fairly cheaply on ebay. Poke that down and have a look. Going back to the inspection hatch if you have one . I would remove that now and have a look. Nothing like the MK 1 eyeball.

Yes, its probably some daft stainless steel tank like on this boat. I much prefer integral with a nice large access hatch but ( Progress :( ) has got in the way again. This boat has stainless tank and if it starts to leak I have a hell of a job and much dismantling to get at it and no way can I see inside it ever. So far so good and we always drink straight from the tank but integrals are way better imo.

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4 minutes ago, Slim said:

Where is the breather relative to the filler, higher or lower? If lower I would expect the level to drop as water drains out the breather. Elsewhere you have said that you're reluctant to use a dip stick for fear of dirt. Wait until you take the inspection hatch off (assuming you have one) I suspect you will be surprised. I always use water containers for my drinking water. You can pick up a waterproof endoscope with light fairly cheaply on ebay. Poke that down and have a look. Going back to the inspection hatch if you have one . I would remove that now and have a look. Nothing like the MK 1 eyeball.

the breather is at the same height.

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53 minutes ago, moiuk said:

Its stainless steel, but integrated into the bow so I have only limited access.

Yes it's fitted into the bow but if you use the term "integrated" you'll just confuse everyone because they might think you have an integral tank.

  • Greenie 1

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12 hours ago, zenataomm said:

Probably nothing to do with your problem ... but

 

Years ago I was called out to a similar problem.

The water tank wasn't integral and had been formed from thin gauge steel sheet.

Cutting to the chase, due to poor ventilation and a healthy pump a partial vacuum was formed which in turn partially collapsed the tank.

 

We had to cut the top off in order to hammer the collapsed side out, we also put in a bracing strap to strengthen it, and of course increase the ventilation.

Seen it of vehicle petrol tanks a few times.

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12 hours ago, Keeping Up said:

The vent on my water tank is identical to the one on my diesel tank; the builder said that the advantage of the flame arrested gauze is that it ensures no insects can get in. However a disadvantage is that on anything fast like the hose at a Thames lock, the air cannot escape quickly enough when filling so that it appears to be full (ie the inlet overflows) when it is actually less than half full. Could this be the OP's problem?

On our previous boat, the vent line went down and up and so contained a lot of water. It was impossible to fill to full. I wonder if the OP is only getting the tank 1/3rd full and is being fooled by the tank level gauge (in the photo) which measures the head of water in the tank - and will give wrong readings if there is a vaccum being pulled as the tank is used.

Sorting the vent line allowed us to fill the tank to full.

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