Breville Dual Boiler - low flow, slow brew pressure

Equipment doesn't work? Troubleshooting? If you're handy, members can help.

#1: Post by davedimes »

Hey All - Long time since I've been on the boards. My friend gave me an old model Breville dual boiler - the one you cannot manually drain - and there are some issues I'm trying to isolate.

When pulling a shot, the pressure will not ramp. Without a portafilter, the water flow is much less than I expect. With the blind backfill portafilter insert - the pressure will ramp... eventually.. definitely not during preinfusion and only 10+seconds into the shot and very slow. The pressure does eventually reach 10 and the OPV seems to kick things back into the pan. Steam and hot water pressure seem to be ok. Solenoid buzzing does not seem too bad.

So... is this a 'weak' pump? Or maybe a clogged line that needs descaled? I took it apart and the lines look pretty nice.. not a lot of evidence of scale but I did not take anything components apart.

Thoughts on how to proceed from here?



#2: Post by cmin »

Likely failed pump on its last breathe. Cheap to replace. Might as well do opv as well. Or do the brass mods which I have on my 920XL. Way better than stock replacement pump and opv I did prior, especially with the slayer mod which still worked kinda wonky with those replacements. ... -valve-opv ... 3782929227

davedimes (original poster)

#3: Post by davedimes (original poster) »

Thanks cmin.

I ordered the pump and considering the brass upgrades as I can't find the regular OPV in stock anywhere. Any chance that the OPV is bad as well? It does ramp to correct pressure, just takes a long time. And when trying to pull a shot I do see some pulses in the water reservoir.


#4: Post by cmin » replying to davedimes »

Honestly not sure but it's possible, was having issues with my machine and even though replaced pump and opv was still wonky (and had already done solenoid). So no clue if I just got double unlucky with two bad parts again? Redid everything with brass pump, vibiemme opv and obviously the brass connector and machine works perfect now and profiling is even better than before replacing the stock parts with stock again.

To me it still sounds like a dying pump, mine would ramp as well and would work with back flushing but shots were terrible. The opv is cheap to replace but yeah if out of stock kinda sol. Would just do brass mods listed above, the connector can take a few weeks to deliver as shipped from Europe. Big issue with Breville parts right now, even the solenoid has been out of stock everywhere for months but I believe some made one for a Silvia or similar fit.


#5: Post by WWWired »

Hi davedimes :)

cmin is offering great insight for sure :)

In support of cmin comment, it is important to note that the reading on a "Pressure Gauge" is not the pressure a pump is putting out, but rather is a measure of how much "resistance" is currently being overcome in the hydraulic system.

davedimes (original poster)

#6: Post by davedimes (original poster) »

So I put in the new pump - sounds better - but still the same symptoms. What is more clear now is it seems that during the pressure phase there is quite a bit of drip back into the water reservoir. So must be the OPV.. I'll take apart and check the o-ring?

davedimes (original poster)

#7: Post by davedimes (original poster) »

I've been working on this darn machine for a month or two now.. it previously had low water flow so I replaced the pump (did not seem to fix the issue). Then I replaced the OPV because it seemed most of the water during the extraction was going back into the reservoir. That also did little to fix the low flow, but I fiddled around some more and lowered the pressure to 9 --> and now all of a sudden I'm getting too much water flow. See the video below. The pressure is fine if I use a blank, but this sudden rush during pre-infusion.. is that right? Water flow sensor?

*edit: have to add that before this issue I also took off the solenoid and cleaned the bottom/gasket..


#8: Post by mangoie »

Hey, that first burst of water is something I have too on my bes900, so could be normal? (my machine is also acting a little weird)

One test you could do is measure how much water your pump outputs per minute through the grouphead. Without preinfusion should be about 460ml/minute. Sometimes the o-rings go bad under te solenoid valve and block water flow. This suspicion is even more valid if there is a big difference between the output flow per minute between the group and the hot water spout!

Lastly, people often forget that the pressure gauge can "fail" too. It's connected to the group head and can be clogged up if never backflused. Seen too many machines with clogged up meters that were dumped because it "doesn't build up pressure anymore"