# hx machine (bz02) de-csale - syphon/dredge out boiler ?



## jpaul__ (Feb 19, 2016)

I have de-scaled the hx machine I have several times, but it is always difficult to make sure all the fluid is removed from the boiler circuit, so I am contemplating inserting a tube though anti-vac valve hole (6 in left image) to syphon all liquid and any sludge from the base of the boiler.

Has anyone done this does it work ? (I will try syphoning but maybe a syringe will need to be attached to silicon tube I was planning to buy)

The need for doing this was obvious after recent descale where I found there was some greyish sludge from the hot water tap, (2 right image) I do not use this regularly and it does draw water off near the base of the boiler.

[yes these are obviously compromises with respect to a full tear-down of the boiler ]

*Also* can someone explain how the fresh water (with obviously a single pump) is supplied to both top up the boiler circuit and the heat exchanger insert for brewing ?


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## John Yossarian (Feb 2, 2016)

Hi JPaul,

I am using exactly the same approach as tearing it down is time consuming and cannot be done too often. Once you have got the citric acid done its job and dissolved all the lime scale it is a question of patience and repetitions to fully clean up the bottom of your boiler. Several fillings/emptyings will do. I use 50 ml syringe (a smaller one would have driven me crazy) and a normal, not necessarily silicone, tubing.

It seems to do the job. If you would like to make sure you have profoundly cleaned it, you may use some litmus paper to see at what point you get back to normal water pH, should be about 5.5-6 given the CO2 that gets the water slightly acidic.

Good luck and share experience!

Cheers.


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## jpaul__ (Feb 19, 2016)

well I had some issue getting the complete anti-vac out, I had only taken the top off before and inspected the moving part of the valve.

I used a deep 19mm socket over the top of it, machine was cool.

Seemed to be needing a lot of force and I was concerned it might shear, so I then applied cooling spray to the

brass anti-vac, put socket in freezer too (based on brass having a lower expansion rate than copper boiler)

it then shifted.

once I got it out seemed Bezzera had kindly put a spot weld on the anti-vac body (in picture) so I could not separate the two parts where I had expected (I will probably put some silicon grease, molkote 44m when I re-insert in boiler, as opposed to copper grease , poisonous I guess)

I was now able to syphon out the fluid, I used a two core flex about 50cm long where I pulled off the vinyl sheath

cannot see much in the image, but close up with eyes, element was not completery clear, and I wonder if the recent descale had well mixed the acid at the base of the boiler, so I will descale again and maybe leave longer than the 1hour from last time after bringing machine up to temp and turning off.

A bit concerned that leaving acid in a long time could eat through the element.


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## grumpydaddy (Oct 20, 2014)

You should be able to get that spot weld with a baby file


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## El carajillo (Mar 16, 2013)

If you are referring to grease on the thread, why not use PTFE tape ? , this will help seal and prevent binding / sticking.

As GD said a needle file will remove the weld spot.


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## jpaul__ (Feb 19, 2016)

I used ptfe where I broke the anti-vac valve apart, although I have now replaced the complete valve the sputtering has not reduced much from an earlier thread I posted (valve problem need precision grinding like engine valves)

I used grease on re-inserting the valve into the boiler (seal was fine) , being a bit scared by how much torque I needed to apply to remove it, but you are right maybe ptfe would have been better.

Siphoning out the tank via anti-vac, (over) filling directly with descale and then siphoning back out worked fine,

I had found that overfilling by disconnecting high water level had previously caused a lot of fluid (rcd fired) to leave through anti-vac on re-powering machine (only caveat was starting siphon to get descale out)


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## Dylan (Dec 5, 2011)

Did you get a good look inside the boiler to check for serious signs of scale? (shine a light in there and have a look in the bottom)

If the machine has a build up of scale in the bottom of the boiler descaling solution probably wont be able to dissolve it down to siphoning level.


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## jpaul__ (Feb 19, 2016)

could see the back of the bolts from the lower plate on the boiler - but it is not all clear and still some on the element,

I will start doing it more regularly.

this machine was 2nd hand, and with previous audrey (from new) although I descaled regularly, I never looked inside boiler.

Although removing furring will help with element life/efficiency , as I say I am a bit concerned with potentially eroding metal on the element itself , am using puly descaler, but had previously seen what hg limescale remover (phosphoric acid -different league) will do on brass pipe fittings


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## Dylan (Dec 5, 2011)

I have soaked brass parts in Citric (which I think is what Puly is) for well over 24 hours and it hasn't damaged it at all.

Phos is MUCH more aggressive, but takes a fraction of the time, it also needs to be properly diluted. If you have stuff caked in scale sometimes Citric just isn't up to the task and Phos is necessary.


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## jpaul__ (Feb 19, 2016)

so puly descaler actually lists citric acid/malic acid/sodium citrate

I am not sure what the role of the last 2 is,maybe to give a stronger taste when chemical residue is left.

for citric acid on its own, I guess I should maybe buy 2kg for £10 on ebay rather than puly at ~10packs30g for £10

anyway about the acidity/power

it seems if I dissolve 30g citric in 1 litre water this has a ph of about 2 and would be about 3 times more acidic than a 5% acetic acid (vinegar) solution from supermarket.

If I bought say 75% phospohoric acid (ebay seems in this vicinity) this would be about 30 times more powerful than my 30g citric if I did not dilute it further.

[i used calculators from here ]

Do you have any advice on an appropriate phospohoric dilution or alternatively could increase the concentration of citric ?

I am not sure what other factors come into play too, like having to explicitly neutralize a stronger acid with an alkali/base as opposed to just flushing water ? (like for central heating descale)

obtaining some litmus paper might also be a good way to know objectively what I am putting in the machine .


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## John Yossarian (Feb 2, 2016)

Phosphoric acid is tricky. One needs to be very careful with regard to concentration and timings. Citiric acid at 10 % by weight added at high temperature, 70-80 deg C would do similar job without the risk of overdoing it. Just my personal opinion. I have used both.


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## Dylan (Dec 5, 2011)

Only use phos if it's neccessary. In cases of seriously heavy scale that critic can't manage. There is a member on here who repairs machines maybe called *got his name wrong* who uses phos, if i got the name right he may be able to advise.

Edit: ya can't remember his name.


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## Dylan (Dec 5, 2011)

I think i had his name right but he has deleted his account.

In any case here is a thread that shows the dilution:

http://coffeeforums.co.uk/showthread.php?19464-Nuova-Simonelli-Maxi&highlight=Phos+ratio

It also says it is less aggressive on the copper than critic so make of that what you will


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## jpaul__ (Feb 19, 2016)

Thanks for the link : it sounds a bit arbitrary on the 1:4 dilution suggestion of the phos acid, I think that would make the typical ebay phos acid some 5x stronger than a citric acid 30g/L recipe.

I will buy some pure citric powder online (I guess the brewing specific stuff will not have been adulterated with sulphuric acid say, which is in a lot of the cheaper packet coffee machine mixes) and then try the 100g/L proposal from John.

[ As you probably knew phos acid is the stuff in Coca-Cola so that might be another option







]

I could not find any links/scientific article that easily discusses how much temperature will increase the dissolving 'power'

[ filling/emptying the boiler via anti-vac is easy/targetted vs water tank, I guess I can turn it on for a short time to raise temp]


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## Missy (Mar 9, 2016)

I'm guessing you don't have Yorkshire traders /boyes etc where you are, I pick up citric acid powder for a couple of quid in those places. They generally are in places that sell various household bits and bobs, including soda crystals, borax substitute, paint and haberdashery.


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## Dylan (Dec 5, 2011)

jpaul__ said:


> Thanks for the link : it sounds a bit arbitrary on the 1:4 dilution suggestion of the phos acid, I think that would make the typical ebay phos acid some 5x stronger than a citric acid 30g/L recipe.
> 
> I will buy some pure citric powder online (I guess the brewing specific stuff will not have been adulterated with sulphuric acid say, which is in a lot of the cheaper packet coffee machine mixes) and then try the 100g/L proposal from John.
> 
> ...


I'm not sure how directly the two acids relate in terms of descaling power.

In any case phos is meant to be a lot quicker, so a 5x strength doesn't sound that unusual if it means anything when it comes to this.


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## John Yossarian (Feb 2, 2016)

1-2% wt phosphoric acid should be fine. Phosphoric acid is not oxidizing for copper so it should not be a big deal in the end.


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## JohnPrime (Nov 2, 2014)

Hi,

I bought a very badly-scaled BZ02s a while back. I posted here about the refurb that I did; I split the boiler to speed things up.

A few things I learned were that citric works fine, especially warm (thermodynamics, innit), that impact drivers1 are much kinder

to tight threads than spanners, and that, if you can find a cheap one on ebay, a peristaltic pump makes the whole process a lot faster.

I've got a BZ99 in the shed ready for a repeat of the whole process...

1) One of the little battery Li ones that work well on wheel-nuts. They appear to be agressive, but (angular) impulse = torque x time,

so the threads get much less impulse from a driver than a spanner. The HX came out of the boiler like a charm, with no thread damage

Enjoy. And we want pics


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## jpaul__ (Feb 19, 2016)

thanks yes I had seen your thread in earlier research - I liked the hot melt on the threads in particular (did not figure out how you got it off blow torch hot air gun )

One after thought that just occurred, is that without an endoscope, I should be able to determine from volume of liquid taken out whether the limescale build up is significant, from what I can see it is nonetheless small compared to your bz02.

my Rancilio Audrey had a brass boiler,not sure what the relative merits of brass vs copper in the bz02 are, whether that was one up for Rancilio ? maybe bigger boilers in brass are more expensive to manufacture.

addendum - I am intrigued by your comment on impact wrench, I though they had the possibility of applying a much greater toque albeit over a short period (I have previously used temperature differential a blow-torch on seized on car wheels, that was why I tried cooling the brass fittings with the lower coeff of expansion - although I cannot be sure that helped. I also considered getting the torque wrench out for undoing but I think I read you can damage them used in this way)


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