Hey everyone

First post here. About a month ago I purchased a beautiful used Pavoni Pro and a new Baratza Vario grinder. I've been getting some amazing shots but also some duds. It's been a fun experience figuring out how to make more consistent shots and all that. As someone who prefers vacuum tubes and vinyl to mP3's and CD's this setup is right up my alley .

Unfortunately one Saturday morning I accidently ran it dry (turned on with lever up, came back to the kitchen later to a wet floor - yikes) and like an idiot poured in some cold filtered water and blew the heating element. Blew it apart to be more specific. Yikes.

I replaced the heating element (learned the machine was from 1987), copper tube and thermostat with new parts and I brought it back to life! YES!

However, since then I've been having problems adjusting the older pressurestat to keep the bar around 1. Ive tried adjusting the pressurestat screw (see below for link image) and it heats up initially way too high then after a shot it hovers around .5 bar. Sometimes it goes back up way too high, sometimes not. Is my pressurestat just on the fritz or is it user error?

The pressurestat looks exactly like this one:


Thanks so much in advance, I have more questions but I'm enjoying figuring them out on my own.

JK

Generically speaking those old pressurestat are pretty tough and can take more abuse in relation to the "newer one" but they are not a forever lasting component,
the microswitch can get "sticky" move the mechanism few times and see if is moving nice and easy,
you can use some DW-40 on the hinges if not.
Also have you clean the pipe and make sure that was no sediment flake left inside?
best way to see scale or loose flake is:
after removing a part let it seat to dry, then you will know right the way if you have deposits or not.
you can also try few drops of descaler solution directly in the Pstat pipe
then rinse and blow some air

I have a 1984 Pro, and when I got it a few months ago it had years of scale inside. I used citric acid, changing out the solution daily, for 1 week and that took care of the boiler scale. Inside the pstat was a whole other issue though. I would have thought 1 week of descaling and frequent heating would have cleaned out the scale from the pstat, but it didn't.

So I removed the pstat, removed the microswitch and descaled just the inside of the pstat membrane area. Then taking a narrow straw filled with descaling solution I would insert the straw into the pstat body opening, blow in the new solution, old solution would run out. I repeated that over and over for 1 day, and finally was getting clean descaling solution. After that you might still have some debris inside the body, and continued flushing from sink tap through the straw helps with that sometimes.

Make sure your descale solution is fairly strong if you are using citric acid, because if it gets neutralized you can have citric salts build up that are hard to remove.

As always, Stefano has some good advice there too.

IIRC, our resident chemist, Rpavlis, recommends acetic acid (vinegar) over citric acid for the very reason you state... So you don't get precipitates, especially in small places like pressurestat tubes.

Threadjack alert: I plan to descale my recent Pavoni ebay purchase, it works but has some scale, and I was so impressed by Robert/rpavlis' recommendation for white vinegar, that I have decided to use that. Plus, it's cheap in large quantities.

Sooo, any thoughts against:

1) de-scaling with white vineagar
2) turning on the heater and "pumping" out some blank shots of vinegar as to be sure it gets into all the same places the water went
3) cool, and repeat as neccessary

ON EDIT: Screw it. I just ordered some Urnex Dezcal off ebay and will be done with it. Should I disassemble or pump it through?

-Peter

DanoM wrote: Make sure your descale solution is fairly strong if you are using citric acid, because if it gets neutralized you can have citric salts build up that are hard to remove.

I'm not a chemist and all I can say is what I experience,
personally I will rather make more descaling section of NOT too strong descaling solution
then less with more acid (I personally use the "real descaler acid which is stronger then just citric)
a good ratio is 1 to 10 using "the Italian Descaler"
I personally can stand the smell that vinegar leaves behind and I don't think is that stronger
at lest for serious scale buildups

also the acid will eventually damage the metal and happens often that an heating element already aged or somewhat stressed, could start dispersing to ground after a descaling job is done.
An old trick that I was though is to use some baking powder after you are done with the descaling to neutralized any remaining (??)
this part Pavli can kindly perhaps explain in details what and why

Directly channeling the man himself ...

rpavlis wrote:It is common for calcium carbonate deposits to form in the tubes leading to pressurestats and to sight gauges. In my humble opinion, the best way to deal with this is to dilute white vinegar about 1 to 1 with water and fill the machine with this. Put on the lid and bring up to pressure. Let the machine cool, and, without draining, bring up to pressure again. Do at least three or four heat cool cycles. The pressure drives the liquid into the tubes, and the liquid moves back and forth inside the thin bore tubes.

Calcium citrate (from fully neutralised citric acid) is fairly insoluble. When trying to remove calcium carbonate from small diameter tubes this can result in replacing insoluble calcium carbonate with insoluble calcium citrate! Calcium acetate, on the other hand is highly water soluble. Thus acetic acid--vinegar-- is a far better choice when blockage of small tubes is involved.

After doing this, you will need to drain the vinegar solution carefully, and then fill and empty the boiler at least three or four times to remove the last traces of acetic acid from the boiler. (Acetic acid has a substantial vapour pressure, and residual acetic acid can make espresso that smells like a salad.) However, four rinses generally lowers the acetic acid content to levels that are not detectable, if one drain the reservoir carefully each time.

pcrussell50 wrote:IIRC, our resident chemist, Rpavlis, recommends acetic acid (vinegar) over citric acid for the very reason you state... So you don't get precipitates, especially in small places like pressurestat tubes.

Yeah, I've read rpavlis's comments on the precipitates before, so that's why I like to make my citric acid solution a little stronger.

I hate the smell that vinegar leaves behind, and have to do several more flushes of clean water, followed by more flushes until it's gone. I don't descale much and have citric acid around for other uses, so I just make sure my solution is good and sour. Post any acid descale a quick baking soda solution rinse is great. Still baking soda doesn't take care of all the vinegar smell for me without making a slurry and leaving it overnight though so I stay away from it.

Professional descale solutions are the best really.

If you need to do a very time-consuming and difficult descaling job new PSTATs aren't that expensive. On an old PSTAT you want to keep it may be worth applying vinegar to make sure the descaling really works. I'm thinking of a vintage PSTAT I have for the Cremina I'm restoring. Those things last forever if you service them.

It really is a good idea to obtain a copy of the water analysis from one's municipal water supply if one live in a place that provides one. You should be sure that there is not a lot of sulphate in the water, especially if you do a lot of steaming. Calcium sulphate scale is MUCH more difficult to get rid of than calcium carbonate.

Acetic acid is a somewhat weaker acid than citric. That is a good thing. It is also a smaller molecule so it diffuses more rapidly. Because it has a substantial vapour pressure, espresso can be like a salad if one fail to rinse adequately after using it. Less than four thorough water changes and you are apt to have problems. Also it is a good idea to shake the machine a bit after putting in rinse water. I always have filled them completely. Espresso that tastes like a salad is not a good thing. Citric acid is used in commercial descalers simply because it is easier to ship around solids than liquids, not because it is better.

The reason why some advocate putting soda into a machine that has just been given an acid "descale" is because a large fraction of metal carbonates are insoluble. This should result in a thin protective carbonate layer over certain metals such as zinc and zinc alloys.

If descale water be blue you should realise that the blue colour is almost certainly due to cupric ion--you are slowly dissolving your boiler!!!

Many claim that there are delicious flavours extracted by using water with high levels of Ca and other ions. In my town there has always been a flavour in our tap water that makes our tap water taste somewhat like club soda. If one have to descale at all frequently one should take measures to use water other than what you are using. I prefer distilled water. There are huge concentrations of ions already in coffee beans, especially potassium, there is also substantial calcium and Mg so that distilled water espresso is NOT ion free. Strangely, by the way, the club soda flavour of our municipal water is still detectable in espresso made with it. I find that unpleasant.

Thanks so much everyone for the replies. Very helpful!

Best,
JK