Accumulator Tanks

[pyrojames]

Am I missing something or is there next to no difference between the "expansion tanks" screwfix sells for £19 and the accumulator tanks that swindleries sell for £80? The swindleries certainly aren't stainless or the like.

 

[Billjratt]

All you're doing is creating a compressible bubble of air in the system between the pump and the tap. Plastic is good. Screw it into the bilge and forget but leave access to the valve at the top if there is one, or "T" junction at the bottom.

 

[pvb]

They're basically similar. You might need to check the connection size on the Screwfix model.

 

[Artemis_C2121]

Hi James

Very curious myself as my jabsco 2ltr continually leaks from the naff unions they use ending up with fresh water swilling around under the aft cabin berth.

Will split the difference with you if we get one and see if we can cobble it together if not we have lost a tenner instead of £20 each.
Also have a screwfix trade centre close at hand may see if i can have a look at one without buying it will let you know
Neville

 

[bobstrawson]

You could actually make one from anything, dependent on the pressure in the system. For instance if you had the room you could put a brass plumbers TEE joint in the line, it doesn't really matter where but near the pump would be good, and put a piece of sealed pipe coming up vertically behind somewhere convenient. It is only to trap air so it must be sited so that the air can't escape. The better ones that you buy have a rubber membrane inside them to stop the air leeching away. From memory, as I haven't had dealings with one for some time, they usually have an air bleed valve in the form of a schraeder valve on top so that you can presurise/de-pressurise, the top of the membrane and thus the system.

 

[pyrojames]

Well, I have little doubt that they will be fine and plan to fit them to my boat, but not until April/May. If you can wait that long I shall report back. I was just unsure if I was missing something fundamental...

 

[pvb]

[ QUOTE ]
You could actually make one from anything, dependent on the pressure in the system. For instance if you had the room you could put a brass plumbers TEE joint in the line, it doesn't really matter where but near the pump would be good, and put a piece of sealed pipe coming up vertically behind somewhere convenient. It is only to trap air so it must be sited so that the air can't escape. The better ones that you buy have a rubber membrane inside them to stop the air leeching away. From memory, as I haven't had dealings with one for some time, they usually have an air bleed valve in the form of a schraeder valve on top so that you can presurise/de-pressurise, the top of the membrane and thus the system.

[/ QUOTE ]For them to work properly, they do need a pressurised membrane. A bit of pipe with air in it wouldn't be as effective.

 

[bobstrawson]

PVB is quite right, I made one for a hydraulic system to damp out pulsing but with water, without a membrane the air would dissolve into the water.

one thing to look out for is that as the system is pressurised the pumps sometines leak back causing them to cycle a few times to re-pressurise. It can get on your nerves a bit in the dead of night, it might pay to put an extra non return valve straight after the pump. Unless you switch it off as soon as you've used it, of course.

 

[johnnys]

James,
just a word of caution, expansion vessels for central heating systems are not usually lined. The steel wont rust as the water inside is not replaced and eventually loses its oxygen. One required for a fresh water system either needs to be plastic or have a liner in it, hense the extra cost!

 

[pvb]

[ QUOTE ]
James,
just a word of caution, expansion vessels for central heating systems are not usually lined. The steel wont rust as the water inside is not replaced and eventually loses its oxygen. One required for a fresh water system either needs to be plastic or have a liner in it, hense the extra cost!

[/ QUOTE ]There needn't be an extra cost - look at this one for example - only £19 and has full butyl rubber liner.

 

[narooma]

....or you could upgrade to a modern Jabsco pump which manages to do without one.

 

[johnalison]

I've got through four tanks in the F/W system in 8 years. the rubber membranes seem to last no time at all and need to be pressurised to the stated pressure with a cycle pump. My first plastic tank split at the vent hole and when my present one goes I'm going to get one of those expensive water-pumps to save the bother of hanging upside-down in the cockpit-locker twice a year.