How safe is running water through a zinc housing?

[simonp]

I've been looking at pressure relief valves again, and have found a cheapish pneumatic one, but the housing is made of zinc. I have no idea wether zinc would be safe to run water to the boiler through, so was hoping someone here can enlighten me.

[matts]

Sorry, what for? Are you talking about plumbing in a machine

Cheers
Matt

[simonp]

No, it is for giving accurate settable pressure to the boiler from the pump, similar to what Greg Scace did, but I'm looking for a cheaper option.

[aloening]

If you live in an area with acidic water then the Zinc will corrode pretty fast. So that means Zinc in your coffee and boiler. In a hard water area you will get a lot of deposits in the valve which will eventually stop working.

Also check the pressure relief arrangements - if you pressurise the boiler and then heat it up without allowing some water out you will most likely crack the boiler or at least cause some leaks somewhere.

There is a good reason that these machines use brass and stainless steel components. My first espresso machine (A Gaggia domestic of about 1987 vintage) lasted around 9 months before the zinc boiler corroded away. Current Isomac Tea is all SS - so no worries.

Go for SS every time!

Adrian

[simonp]

If you live in an area with acidic water then the Zinc will corrode pretty fast. So that means Zinc in your coffee and boiler. In a hard water area you will get a lot of deposits in the valve which will eventually stop working.

Also check the pressure relief arrangements - if you pressurise the boiler and then heat it up without allowing some water out you will most likely crack the boiler or at least cause some leaks somewhere.

There is a good reason that these machines use brass and stainless steel components. My first espresso machine (A Gaggia domestic of about 1987 vintage) lasted around 9 months before the zinc boiler corroded away. Current Isomac Tea is all SS - so no worries.

Go for SS every time!

Adrian

I live in a hard water area, so it sounds like deposits would be the main worry.

The valve would go between the pump and the boiler (as does the current one, effectively) so the boiler is only ever under pressure during pumping. The valve would just open at the set pressure (around 9 bar) which would vent the excess back to the water tank (again as doe sthe current non-adjustable one).

Yes, stainless steel would be better, but I am weighing up the price difference between £105 and £20, hence my interest.

[simonp]

Sorry for the multiple posts, I kept getting a PHP fail message, so thought it hadn't gone through.

[aloening]

Hi Simon,

Which valves are you looking at - seems the SS valve is very expensive. There is likley to be a better solution.

[simonp]

Hi,

I am just after a settable pressure relief valve, the one in the Silvia can only be adjusted by latering the thickness (i.e. sanding it thinner!) of an additional copper washer. The valves I was looking at are for air really, but should also work with water, as the inlet is cold water. It is possible a brass valve from another espresso machine would also work, but it is finding a part number etc that is tricky,

[motoman]

Simon, why are you not using filtered water? Not only will it prevent corrosion it will also make the coffee taste better. I have a filter kettle and in 3 years there is no sign of scale at all and I live in a hard water area too.

[quink]

I have a filter kettle and in 3 years there is no sign of scale at all and I live in a hard water area too.

I'm going to have to second this, nothing but britta filtered water in my kettle and no scale whatsoever and it must be 3 years old by now. Although I cant taste any difference in the water its obviously doing something.

[simonp]

I do use filtered water through a Britta filter, but it only takes out some of the hardness, there is still a reasonable ammount there. The kettle still has to be de-scaled every now and then.

[aloening]

The effectiveness of filters depends greatly on the hardness of the water. Where I live the water is so soft there is no deposits in my kettle with 12 years use - so far. In some other areas an ion exchange resin will be used up in weeks. Thus I have not yhet bothered to replace the filter that my Tea came with.

Simon - I will have a quick look through some of my sources for a suitable valve.

[fiend]

I live in London, and my kettle is pretty crusty. Apparently the water is a lot softer in the South West and in Scotland, so I get Scottish bottled water from Tesco. I just checked through my last bill, and 6 2 litre bottles (12 litres total) from Perthshire cost £1.88. That's quite a few ristrettos in there, and there doesn't seem to be any limescale buildup inside my machine.

[simonp]

In Wiltshire a lot of the water comes from underground wells, and is very hard, so yes the ammount the filter takes out still leaves quite a lot of harness in, but at least this helps the taste of the coffee, as I understand that too soft water gives a poor taste.

[quink]

but at least this helps the taste of the coffee, as I understand that too soft water gives a poor taste.

I can notice the difference at work but its probably from a different reservoir as it 25 miles away, not filtered and preground beans doesn't help. The kind of taste that makes you think, whats the point of all the effort, but the guys at work really love it when I bring it in.