# Brass shower plate holder - will it react with something up in there?



## Vital Spark (Jul 1, 2017)

So I bought a brass shower plate holder for my Gaggia classic as the standard aluminium one was starting to look like a bit of mouldy mud. I'm planning to do a lead test on it to make sure it is no/low lead brass.

Anyway, I knew it wasn't coated bass before I ordered it and thought that as the group-head is (coated?) brass, it should be compatible for long term contact. However, putting it in just felt wrong. Won't that much uncoated brass react with something in there? Brass has a lot of zink, and in a wet environment with other metals around, especially aluminium, that is crying out for a reaction to occur.

Am I over thinking this? I realise I was replacing the original as it was degrading, but at least there I knew what was degrading (even if I wasn't happy about it). Now I am not only worried about lead, but also what might be happening between the screws, the boiler just above...


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## Mrboots2u (May 10, 2013)

Your over thinking this


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## Vital Spark (Jul 1, 2017)

Mrboots2u said:


> Your over thinking this


But why? Where else is uncoated brass only a few cm from aluminium and both are frequently in contact with the same water?


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## DaveP (Jul 14, 2017)

Brass has been used in plumbing for quite some time now.... but it may discolour with acid cleaners


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## Vital Spark (Jul 1, 2017)

DaveP said:


> Brass has been used in plumbing for quite some time now.... but it may discolour with acid cleaners


Yes, brass is used in plumbing, but aluminium is generally not. The few places where it is used (eg tanks on boats) it is a problem to find a compatible low cost metal which will not react with the aluminium when in constant contact (either direct contact or contact via water) and in such situations a brass value or connector on an aluminium tank is not a good idea. I was wondering why, or if, this is different.


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## urbanbumpkin (Jan 30, 2013)

What are your concerns with this?


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## timmyjj21 (May 10, 2015)

The entire lower half of the boiler is chromed brass, while the upper half is aluminium. The dispersion plate is not in direct contact with aluminium. The aluminium boiler will get pitting at the seal over time no matter what, and having a solid, durable, easy to clean dispersion plate is of significantly greater importance.


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## Vital Spark (Jul 1, 2017)

urbanbumpkin said:


> What are your concerns with this?


That the brass will cause any aluminum in contact with it (direct or via water) to corrode away. OR if there is a stronger anode metal in the lower half of the system (which might explain some of corrosion of the original screen holder) then that will leach the zink out of the brass.


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## Vital Spark (Jul 1, 2017)

timmyjj21 said:


> The entire lower half of the boiler is chromed brass, while the upper half is aluminium. The dispersion plate is not in direct contact with aluminium. The aluminium boiler will get pitting at the seal over time no matter what, and having a solid, durable, easy to clean dispersion plate is of significantly greater importance.


How is it not in direct contact, when the pump is off does the water pressure reduce to an extent such that the boiler is no longer in any water contact with the shower screen at all? That might explain why it is OK to use, but only if it is certain the water bond is completely broken - broken to the extent that the two metals are electrically isolated from one another.

Uncoated brass in the vicinity of aluminum is like using a toaster in a bathroom: it might be OK in some situations, but in general it should always be avoided.


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## timmyjj21 (May 10, 2015)

Solenoid valve. When the machine is off, it isolates the group head from the boiler. The seal should be water tight.

As mentioned by Mrboots2u, I also think you are over thinking this.


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## DaveP (Jul 14, 2017)

Ahhh.. but its Saturday and the stainless bolts that attach the brass to the aluminum come into effect, so I shall invoke Trumpington's Variations


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## timmyjj21 (May 10, 2015)

Ah, my mistake. I didn't think Trumpington's Variations affected metallurgy, but my physics is rusty (pun intended!)

What you really need to be concerned about is that Gaggia is too cheap to use stainless bolts on the boiler, so you instead have poor quality ZINC galvanising on the mild steel bolts that are no doubt corroding as we speak...

Unless the OP has one of my refurbs from when I lived in the UK? There should be quite a few in circulation that I replaced with stainless!


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## Vital Spark (Jul 1, 2017)

I appreciate it is just a coffee machine, but if you have ever seen a fuel leek or even just a water leak form someone deciding that the brass valve fits just fine into the aluminum fitting (until there is so little left holding it it falls out) then maybe it wouldn't be so amusing.

RE the bolts, it was actually when I picked those up to attach the brass plate and wondered 'are these really stainless, seems not' that I then wondered about constant water contact with with boiler. The three way valve explanation is reassuring, thanks


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## El carajillo (Mar 16, 2013)

1. You are over thinking it.

You already have a brass steam valve attached directly to the boiler.

A very small proportion of lead is added to brass to aid machining ( not sufficient to be harmful)

The "galvanised " bolts could possibly have been deliberate to act as a sacrificial anode. ( lessen the effect on the boiler)

Using aggressive descaler and strong solutions of cleaner in the head strip the natural protection the water and time has deposited inside the boiler and on the dispersion plate

Using suitable water significantly reduces boiler scaling.

Removing the dispersion plate and scrubbing with a brush& mild detergent removes oils but does not strip back the zinc from the brass leaving the pink copper.

Just concentrate on making good coffee:good:







If the boiler is eaten away you will hardly have a flood with less than 100 ml of water.
























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