Expansion Tank!?

[Zoeb]

Hi all ... 2 questions...

 

We have a flo jet "quiet quad" driving our freshwater tank.

 

There is what I think an expansion tank also connected to this as the water leaves the bow to travel to the boat...

 

1. Can anyone explain to me what this tank does please? (Pics attached) am struggling to understand its purpose.

2. when we are using the shower the flo jet pump cuts in and out every 5 seconds or so - (there are no leaks) - is the cutting in and out normal?

Thanks!

With pics

[Tiggs]

It has air one side of a rubber diaphragm and water the other side. When you open a tap the water is pushed out by the air. When the water pressure drops the pump starts and pushes the water out though the tap and against the diaphragm until the pressure rises above the pressure switch setting. It cycles like this.

 

5 seconds is probably ok but I'm not familiar with that particular pump since we always used centrifugals (which hardly anyone else did). The reason for having an expansion tank is so that the cycle of on/off is not too short and so that you don't just have a pump which you switch on manually and then cavitates and destroys itself when you don't switch it off.

 

You can get pumps not that do not need a tank - not sure how these work.

Edited April 6, 2016 by Tiggs

[ditchcrawler]

I would suggest your air charge pressure is not correct in the accumulator.

[Iain_S]

(snip)

You can get pumps not that do not need a tank - not sure how these work.

 

They are variable speed, so (are supposed to) run slowly when there is a low demand, i.e. not a lot of pressure drop. The say "Do not fit an accumulator" in their installation instructions, but I cannot see what harm an accumulator would do in such a system.

[boat fan]

That vessel is an accumulator. Its purpose is to reduce pump cycling ( switching on / off ).

 

It works just like Tiggs has explained.

 

I don`t know what model Flo-jet Quad you have , but I have this one :

 

 

 

 

 

This pump does not require an accumulator.

 

With this pump you can fit one , but its not really required.

[Tony Brooks]

 

They are variable speed, so (are supposed to) run slowly when there is a low demand, i.e. not a lot of pressure drop. The say "Do not fit an accumulator" in their installation instructions, but I cannot see what harm an accumulator would do in such a system.

 

Others have an extra low flow rate PRV inside the pump set to a little below cut out pressure. When this some water is returned to the inlet side of the pump so, with an outlet open, the combine flow is supposed to be large enough to prevent any pressure rise. Some makes of these pumps also say do not fit an accumulator and I also do not see the harm it will do.

 

When I phoned the company on behalf of a reader and asked for their technical department I queried the "do not use an accumulator" bit and as far as I can see was just given a bit of a sales script and bullshine, no technical explanation for why not. I can see the dead hand or marketing producing those words.

[NMEA]

With those type of pumps I think there has been a miscommunication between the techies and the people who write the marketing blurb, they seem to have misinterpreted "not required" as "contra indicated" so a myth has developed.

[waterdog]

Thanks for posting this Zoeb, we have had similar issues on our self managed share boat and have been trying to get to the bottom of it.

 

The boat is similar in set up to your picture but with a shurflo pump and a red round ball type accumulator located next to the water tank in the bow.

The pump will run randomly for about 5 - 7 seconds every half hour or so even when there is no demand for water.

I have checked everywhere I can think of and there are no indications of any leaks in the system, I even spent a couple of hours replacing the electronic flush valve in the thetford as one of the group thought there was water leaking into the toilet bowl. This made no difference whatsoever.

 

Last night I closed the water shut off valve (which is only about a foot after the pump) and after about 25 minutes the pump ran again for a few seconds, this to me indicates the problem is at the pump / accumulator end. The pump is relatively new looking but the accumulator is showing signs of age, do they have a lifespan ?.

 

While now fairly confident there are no leaks filling up the bottom of the boat with water it is still something I'd like to get to the bottom of, one of the issues is that if anyone is sleeping in the forward cabin then the noise of the pump disturbs them, easily got round though by switching the pump off overnight.

 

I would be really grateful if anyone can offer any other suggestions or advice,

 

Thanks.

 

Sorry for the hijack Zoeb,

 

Waterdog.

[alan_fincher]

Last night I closed the water shut off valve (which is only about a foot after the pump) and after about 25 minutes the pump ran again for a few seconds, this to me indicates the problem is at the pump / accumulator end. The pump is relatively new looking but the accumulator is showing signs of age, do they have a lifespan ?.

 

So the sequence you have along the pipe is.....

 

1) Cold water tank

2) Pump

3) accumulator

4) A stop valve you have closed

 

Correct?

 

And the pump is still cycling intermittently, but with no water leaks along the bits I have just described?

 

If so, I would say that water must be getting back in the "wrong" direction within the pump, so I think it is a pump fault.

 

An accumulator that is old, and will not pressurise properly would not cause this symptom, I think, unless water is actually leaking out of it

[waterdog]

 

So the sequence you have along the pipe is.....

 

1) Cold water tank

2) Pump

3) accumulator

4) A stop valve you have closed

 

Correct?

 

And the pump is still cycling intermittently, but with no water leaks along the bits I have just described?

 

If so, I would say that water must be getting back in the "wrong" direction within the pump, so I think it is a pump fault.

 

An accumulator that is old, and will not pressurise properly would not cause this symptom, I think, unless water is actually leaking out of it

 

Yup, that is exactly it Alan. I shut the valve last night and the pump still cycled. There are some rusty bits on the accumulator with the paint flaking but no sign of water leak nor any damp patches underneath.

 

Pump just cycled while I am typing this, main valve open now though.

[Zoeb]

Thanks for posting this Zoeb, we have had similar issues on our self managed share boat and have been trying to get to the bottom of it.

 

The boat is similar in set up to your picture but with a shurflo pump and a red round ball type accumulator located next to the water tank in the bow.

The pump will run randomly for about 5 - 7 seconds every half hour or so even when there is no demand for water.

I have checked everywhere I can think of and there are no indications of any leaks in the system, I even spent a couple of hours replacing the electronic flush valve in the thetford as one of the group thought there was water leaking into the toilet bowl. This made no difference whatsoever.

 

Last night I closed the water shut off valve (which is only about a foot after the pump) and after about 25 minutes the pump ran again for a few seconds, this to me indicates the problem is at the pump / accumulator end. The pump is relatively new looking but the accumulator is showing signs of age, do they have a lifespan ?.

 

While now fairly confident there are no leaks filling up the bottom of the boat with water it is still something I'd like to get to the bottom of, one of the issues is that if anyone is sleeping in the forward cabin then the noise of the pump disturbs them, easily got round though by switching the pump off overnight.

 

I would be really grateful if anyone can offer any other suggestions or advice,

 

Thanks.

 

Sorry for the hijack Zoeb,

 

Waterdog.

 

no problem waterdog - keen to get as much info as possible...

 

 

That vessel is an accumulator. Its purpose is to reduce pump cycling ( switching on / off ).

 

It works just like Tiggs has explained.

 

I don`t know what model Flo-jet Quad you have , but I have this one :

 

 

 

 

 

This pump does not require an accumulator.

 

With this pump you can fit one , but its not really required.

 

thanks boat fan, here is our pump and some other pics if this helps diagnostics.

 

 

Got chatting to someone last night and they also think this is something to do with the pressure, am going to have a closer look at the weekend and may take a pump to it.

 

I don't think it is anything to worry about, but also want to get used to normal and non normal sounds for future...! Everyday is a learning curve.

...

[ditchcrawler]

 

Others have an extra low flow rate PRV inside the pump set to a little below cut out pressure. When this some water is returned to the inlet side of the pump so, with an outlet open, the combine flow is supposed to be large enough to prevent any pressure rise. Some makes of these pumps also say do not fit an accumulator and I also do not see the harm it will do.

 

When I phoned the company on behalf of a reader and asked for their technical department I queried the "do not use an accumulator" bit and as far as I can see was just given a bit of a sales script and bullshine, no technical explanation for why not. I can see the dead hand or marketing producing those words.

Lets face it an accumulator is nothing different to a pocket of air trapped in the calorifier. So are they saying their pump wont work with a horizontal calorifier where you may not be able to get all the air out?

[boat fan]

Its a puzzling problem Zoeb .

 

 

 

If so, I would say that water must be getting back in the "wrong" direction within the pump, so I think it is a pump fault.

 

I believe Alan has identified the problem , you appear to have some back flow.

 

It`s not very likely , but is there an inline non - return valve fitted after the pump ?

 

I had an issue of pump cycling at home , where the non - return valve was faulty , causing back flow.

[Zoeb]

hmmm, ill give it some proper thought and diagnostic this weekend - hard to do when at work all day!

 

We also have a problem with our shower pump...the water is flowing up into the sink before passing out through the usual exit! We have to turn the pump on and off every 10 seconds to stop the sink overflowing and let the water catch up with itself.

 

oh dear....

[Tiggs]

hmmm, ill give it some proper thought and diagnostic this weekend - hard to do when at work all day!

 

We also have a problem with our shower pump...the water is flowing up into the sink before passing out through the usual exit! We have to turn the pump on and off every 10 seconds to stop the sink overflowing and let the water catch up with itself.

 

oh dear....

Outlet in side of boat not big enough or partially blocked I would guess - poke a stick in it (from the outside) - if that does not work disassemble and clean.

Edited April 7, 2016 by Tiggs

[WotEver]

Outlet in side of boat not big enough or partially blocked I would guess - poke a stick in it (from the outside) - if that does not work disassemble and clean.

Which is why caravans always have separate outlets for shower and sink.

 

Tony

 

Edit for spilling

Edited April 7, 2016 by WotEver

[boat fan]

Outlet in side of boat not big enough or partially blocked I would guess - poke a stick in it (from the outside) - if that does not work disassemble and clean.

 

 

Which is why caravans always have separate outlets for shower and sink.

 

Tony

 

Edit for spilling

 

Does this mean you are allowed to discharge shower water overboard , or am I misunderstanding this ?

[ditchcrawler]

 

 

 

Does this mean you are allowed to discharge shower water overboard , or am I misunderstanding this ?

Yes

[boat fan]

Yes

 

Thanks ditchcrawler ,

 

That would be a $ 30 ,000 max . penalty here ......

Edited April 7, 2016 by boat fan

[Zoeb]

Outlet in side of boat not big enough or partially blocked I would guess - poke a stick in it (from the outside) - if that does not work disassemble and clean.

 

perfect... there is another outlet not in use from the shower area...which was converted into a bathtub at some point. All makes sense. All good, we are going to potentially revert back to a shower from bath. Hopefully we can reuse the outlet.

 

thank you everyone. Will try to update the thread when the freshwater pump is diagnosed and fixed!

[David Mack]

I believe Alan has identified the problem , you appear to have some back flow.

 

It`s not very likely , but is there an inline non - return valve fitted after the pump ?

 

I had an issue of pump cycling at home , where the non - return valve was faulty , causing back flow.

 

Well there must be an inline non-return valve fitted within the pump. So you just have a slight leak back through this valve, This could be due to a manufacturing defect, wear, or some debris caught in the valve. But its not really a big problem.

[Zoeb]

Hmm - the water in bathroom was just coming out brown (from cold tap) and flow was spluttery. Then I heard the pump whirring continuously (quieter than normal). Have cut pump off for now but could this be as simple as my water tank has run dry?

 

Well there must be an inline non-return valve fitted within the pump. So you just have a slight leak back through this valve, This could be due to a manufacturing defect, wear, or some debris caught in the valve. But its not really a big problem.

Hi - sorry is this referring to my system or waterdog?

[peterboat]

So the sequence you have along the pipe is.....

 

1) Cold water tank

2) Pump

3) accumulator

4) A stop valve you have closed

 

Correct?

 

And the pump is still cycling intermittently, but with no water leaks along the bits I have just described?

 

If so, I would say that water must be getting back in the "wrong" direction within the pump, so I think it is a pump fault.

 

An accumulator that is old, and will not pressurise properly would not cause this symptom, I think, unless water is actually leaking out of it

I thought the valve was at the tank? not after the pump etc. However my mate a plumber told me that freshwater accumilators are blue because it indicates they are rustproof, and red ones which are cheaper are red for central heating because they normally have anti rust inhibitors running through them.

[David Mack]

Hmm - the water in bathroom was just coming out brown (from cold tap) and flow was spluttery. Then I heard the pump whirring continuously (quieter than normal). Have cut pump off for now but could this be as simple as my water tank has run dry?

 

Hi - sorry is this referring to my system or waterdog?

 

All pressurised water systems will have a non-return valve, either in the pump or separately. So if the pump runs occasionally while you are not running water, then you either have a leak (or a dripping tap) or water is leaking back through the valve.

[WotEver]

 

Thanks ditchcrawler ,

 

That would be a $ 30 ,000 max . penalty here ......

Yes, no grey water tanks over here.

 

Tony