Procon rotary pump: safe to descale using citric acid?

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Kabouter
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#1: Post by Kabouter »

I would like to descale both the HX and the boiler of my Vibiemme Domobar Super HX. It is plumbed in and has a rotary Procon pump. I have read many contradicting statements about potential damage of citric acid solution to the rotary pump. Some say it will damage the pump, but I can think of no other way to descale the HX circuit than using the pump, putting the water feed line into a bucket of acid solution. The boiler could be descaled without the pump by manually draining and then filling it from the top e.g. through the vac breaker. But I would like to schedule preventive half-yearly HX descaling.

What do you do? Do you descale the HX using your rotary pump, or do you know of other ways?

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Compass Coffee
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#2: Post by Compass Coffee »

Just drawn in via pump.
Mike McGinness

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erics
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#3: Post by erics »

Some (all?) Procon pumps are fitted with a sealed ball bearing at the motor end. The cautionary statements you have read were maybe in the context of users soaking the pump in a citric acid solution for an extended time. Even with a sealed ball bearing, I would judge this to be potentially harmful.

Dissolve your citric acid solution (1 Tbl per litre) in hot water and let it cool to room temperature and then use the pump as Mike suggests. Before I would do any of this, I would check for the existence of scale buildup: Checking an E61 Espresso Machine for Scale. On the last page of this link is a pic/description of a descaling "kit" I was putting together. The point there was to descale the mushroom assembly separately because the plating on it has shown the very real tendency of flaking off and blocking some water passages or clogging the gicleur's screen filter.

When descaling your boiler, I would remove the vacuum breaker valve (1/4" BSPP) and install some fittings/hose such that the citric solution can be recirculated - just disconnect the level probe connection and the boiler will intentionally overfill. The vacuum breaker valve you removed can be soaked in the same small container as the mushroom.
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com

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Kabouter (original poster)
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#4: Post by Kabouter (original poster) »

That is good to know, so the bearing should be fine with that. There was also someone who thought that the material that the vanes are made of might be sensitive to acid..

Earlier this week I followed the scale checking guide you mention and descaled the mushroom area already. There was some scale there so that's why I want to also descale the rest of the machine.

Re recirculation: I always thought that recirculating the solution was to be avoided because of the possibility of particles getting into the machine? Also, I guess one might instead be able to recirculate by letting the steam wand (tip off) run back into the container of acid solution? That way I wouldn't have to fit something there.

One more question comes to mind about the overfiling / recirculating bit. I blew the boiler pressure gauge on my previous boiler descaling attempt because my instructions seemed to be missing opening steam wand or tap when pumping with the autofill disconnected. (it caused the safety valve to open but also blew the gauge) Would the gauge be safe when you recirculate in this way, or could there still be a pressure shockwave to knock it out due to the resistance from the tap / steam wand diameter?

[edit: typo]

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cannonfodder
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#5: Post by cannonfodder »

Been descaling with the rotary for years, never had an issue. Your gauge should be safe, just open the steam valve before you overfill the boiler. As long as the boiler is cold the pressure would vent out the vacuum breaker which should be open but for an extra measure of security, open the steam wand.
Dave Stephens

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erics
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#6: Post by erics »

. . . but for an extra measure of security, open the steam wand.
and remove the tip.

I still say that the best way to do this is to remove the vacuum breaker valve and install some BSPP fittings which should be readily available to you in the Netherlands.
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com

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Kabouter (original poster)
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#7: Post by Kabouter (original poster) »

erics wrote:I still say that the best way to do this is to remove the vacuum breaker valve and install some BSPP fittings which should be readily available to you in the Netherlands.
Thanks Eric, I will be trying this solution shortly!