Accumulators - how to test?

[CapitalD]

The accumulator in our boat didn't work after de-winterisation.  Basically the pump runs whenever a tap is open.  The accumulator itself is reading 0 psi from the Schrader valve and, on the bench, pumping air in the valve results in a draft coming out of the bottom.

 

So, am I right in thinking that an accumulator should contain a bladder and mine is ruptured?  Therefore new accumulator time.

 

The existing tank is Xylem (CM288) and sells for around £60.  SeaFlo are offering the same volume (8 l) for £30.  Thoughts about build quality vs price?  Mine is not easy to get to.

[Jen-in-Wellies]

1 hour ago, CapitalD said:

So, am I right in thinking that an accumulator should contain a bladder and mine is ruptured? 

That is a reasonable surmise.

 

1 hour ago, CapitalD said:

Thoughts about build quality vs price?

Make sure whatever you are buying is marketed as suitable for potable water. There are cheaper ones around designed for central heating systems, but their cheapness is because they rely on having corrosion inhibitors in the central heating fluid to prevent them rusting. Ones suitable for potable water have a rust prevention coating inside, which increases their cost. Without this, they will taint the water and rust through in double quick time.

[Tony Brooks]

34 minutes ago, Jen-in-Wellies said:

That is a reasonable surmise.

 

Not saying you are wrong, but if the bladder is "unfurling" itself it will expel air from the bottom but once it has totally unfurled the air flow should stop and the pressure start to rise. Depends on how long the OP pumped for, if for a couple of minutes then you are probably correct.

[Tracy D'arth]

Shake it, can you hear water inside?

[CapitalD]

7 minutes ago, Tracy D'arth said:

Shake it, can you hear water inside?

Yup.

[Tracy D'arth]

17 minutes ago, CapitalD said:

Yup.

Duff.

[CapitalD]

I just discovered that Jabsco sell a service kit (new membrane) for this - a bit more than half the cost of a new unit.  Problem nearly solved.

 

1 hour ago, Jen-in-Wellies said:

That is a reasonable surmise.

 

Make sure whatever you are buying is marketed as suitable for potable water. There are cheaper ones around designed for central heating systems, but their cheapness is because they rely on having corrosion inhibitors in the central heating fluid to prevent them rusting. Ones suitable for potable water have a rust prevention coating inside, which increases their cost. Without this, they will taint the water and rust through in double quick time.

The SeaFlo unit (less than the cost of the service kit) say that its for drinking water.

[Ex Brummie]

A potable water vessel does not have any water in contact with the metal case. They have an internal bladder that contains the water.  They can be identified from the flange at the connection. They are usually white or blue, but there is at least one manufacturer (surecal?) who paint theirs red.

[Tracy D'arth]

13 minutes ago, Ex Brummie said:

A potable water vessel does not have any water in contact with the metal case. They have an internal bladder that contains the water.  They can be identified from the flange at the connection. They are usually white or blue, but there is at least one manufacturer (surecal?) who paint theirs red.

That is why if you can hear water it is busted, the water is in the tin can, outside the bladder.

 

I have found fitting new bladders to be a waste of money and time as the can is usually badly rusted inside before you realise the bladder is leaking.

[MtB]

1 hour ago, Tracy D'arth said:

I have found fitting new bladders to be a waste of money and time as the can is usually badly rusted inside before you realise the bladder is leaking.

 

 

Most have the bladder filled with air (or nitrogen at the factory). The water surrounds it and is in contact with the outer steel casing. On those designed for central heating the outer case is made from mild steel and the corrosion inhibitor is supposed to protect it. For domestic water expansion vessels the outer case is stainless steel which supposedly won't rust, so the fail point becomes the bladder perishing. 

 

I'm told that some have the outer case containing air and the bladder containing the water but I remain to be convinced....

 

[Tracy D'arth]

3 minutes ago, MtB said:

 

 

Most have the bladder filled with air (or nitrogen at the factory). The water surrounds it and is in contact with the outer steel casing. On those designed for central heating the outer case is made from mild steel and the corrosion inhibitor is supposed to protect it. For domestic water expansion vessels the outer case is stainless steel which supposedly won't rust, so the fail point becomes the bladder perishing. 

 

I'm told that some have the outer case containing air and the bladder containing the water but I remain to be convinced....

 

Cut one in half Mike. Its the bladder that hold water, or should!

 

That is why the Schrader  valve is in the top of the can. 

Edited May 11, 2022 by Tracy D'arth

[MtB]

1 minute ago, Tracy D'arth said:

Cut one in half Mike. Its the bladder that hold water, or should!

 

I have, and the bladder contained the air!

 

[Tracy D'arth]

1 minute ago, MtB said:

 

I have, and the bladder contained the air!

Oh!   Confucius he says, confused.  The bladder bottom shows in the pipe connection when the accumulator is removed. So the water  pushes the bladder up and out into the can.

[ditchcrawler]

1 hour ago, Tracy D'arth said:

Oh!   Confucius he says, confused.  The bladder bottom shows in the pipe connection when the accumulator is removed. So the water  pushes the bladder up and out into the can.

That is how mine is, the bit that has the fitting for the water failed and I had a new stainless piece turned up.

 

These are two postings and not immediately connected 

 

An old big one

Edited May 11, 2022 by ditchcrawler