# Forum Home Renovation Metalwork & Welding  Getting a grease gun to use water.

## gros21

Well Im trying to modify a grease gun to use water so I can hydrostaticly test some sure tanks.  
Even with out a nozzle I cant get it to shoot water more than once. Any ideas? 
Is there any tricks ect? 
Ive tried 2 new cheap full size guns a bunnings air one and a normal one from another hardware shop.

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## commodorenut

It's probably the low quality cup (aka bucket) seal on the piston, and the deviation in wall diameter & roundness of the more where this piston seal runs causing the seal to leak and thus not hold the water.  Grease, being much thicker, is far more forgiving of those issues. 
I can't say it would ever be possible to do with a grease gun - you'd effectively be engineering it into a hydraulic cylinder to make it decent enough to pump water. 
What sort of pressure are you trying to achieve? 
Why not look for a cheap (new or 2nd hand) hydraulic cylinder you can re-purpose.   
If it's only low pressure (say 10 bar or less) you can even use a pneumatic cylinder with water in it - just make sure the bore is chromed, or strip it down & dry it out well to avoid rust in storage. 
You can also mount a pneumatic cylinder onto the other end of it - one rod pushing the other, so you can use compressed air to push the water.

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## Whitey66

> Well Im trying to modify a grease gun to use water so I can hydrostaticly test some sure tanks.  
> Even with out a nozzle I cant get it to shoot water more than once. Any ideas? 
> Is there any tricks ect? 
> Ive tried 2 new cheap full size guns a bunnings air one and a normal one from another hardware shop.

  Hmmm, I assume you mean a "pressure tank" not a "sure tank". 
Just fill the tank completely with water then connect the grease gun with grease in it to the tank and inject grease into the water. This will do exactly the same thing as injecting water as you can't compress a liquid with a grease gun. Liquids can be compressed but it would take a great deal more pressure than a grease gun would produce. The only issue is you would have to clean the grease from the tank afterwards, but there wouldn't be much.

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## gros21

Yea sorry it’s an air tank. I want to test it to 250psi-300psi. As my system uses 200psi and the tanks I have are rated at 150psi (well the gauges that came with them are 150psi)  
Tanks are 10gallon (47l)  
Issue is if I used grease would I’d be worried about it getting into the gauge.  
I’ve seen it done on YouTube no specs or real tips.  
To be honest after the day I’ve had I’m half tempted to just bridge the pressure switch out on the compressor and force the last bit as air.  
Doesn’t grease/oils at ignite at certain pressures?  
Would an oil work in a grease gun? 
As it would be eas*ie*st to get out.

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## commodorenut

If you only have 1 or 2 tanks to test, it may be worth paying to have them done professionally?  Can't hurt to ring up & get a quote.  I wouldn't like to be in the vicinity of a used tank that lets go at 300psi.   We pressure test all sorts of things at work, some over 10,000psi & you'd be surprised how "low" pressure (such as 200psi) can still cause massive damage. 
Is the gauge digital or analogue?  If it's analogue, then the grease won't affect it, even if it gets in, as it will still move with pressure.  The analogue gauge works by having a hollow copper "banana" that is at the tank's pressure - the higher it gets, the more it wants to straighten out.  One end is fixed, and the other is attached to a gear that drives the needle.  It doesn't matter if air or grease gets into it - you'll still get the same reading, as the grease won't compress. 
If they're full of water, there's little chance of the grease getting in anyway - and it should come out quite easily - especially if where you drain is the same place where you are injecting the grease.

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## gros21

There 2 new tanks. Used tanks are rated at similar pressure but are of unknown condition.  
But I am going over there specs, well over what the sticker says. I presume the tank would be rated higher than the other components. But as Im not using them for there intended purpose ect Id like to do a x1.5 working pressure test.  
Its a analogue gauge which I dont care if it fails after this as it was a cheap unit.  
Just long as it works. I spose if any grease does it in there its not going to make it read higher.  
2 indentical tanks that are perfect size for there area they will be housed.

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## Marc

You can test the tanks with your compressor and a long hose, so you are away when they go bang and you can still read the pressure and stop at 200 psi.

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## Bros

For my opinion the first step is unscrew the plug on the end of the tank and get a good light and visually inspect the internals. If it is heavily rusted ditch it. If not then get it professionally tested but I doubt anyone would do it without an original test certificate.

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## Whitey66

> You can test the tanks with your compressor and a long hose, so you are away when they go bang and you can still read the pressure and stop at 200 psi.

  Water is much safer at 200 psi than air is. Because air is compressible and water isn't, if it let's go with water it will probably just split the tank. If it lets go with air it will probably shoot shrapnel everywhere as the compressed air escapes.
Has it got a plate welded on it or is the tank stamped somewhere showing the max pressure etc. Sometimes stamping gets painted over making it hard to read.

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