Backflushing... please explain what it is

[Beavis]

I have a 2 year old Silvia, manufacturer says do not back flush. Dan says "no problem". I do not know what it is exactly, what does it accomplish and I assume there is apart you have to buy to do this? Thanks.

[Randy G.]

I have a 2 year old Silvia, manufacturer says do not back flush. Dan says "no problem". I do not know what it is exactly, what does it accomplish and I assume there is apart you have to buy to do this? Thanks.

If you take a look at my website, there are not only instructions as to how to backflush, but full and detailed explanation/lesson as to the whats and whys of the process, specifically aimed at Silvia, but relevant to most home, single boiler machines with a 3-way valve (all links will be in the right-hand column).

http://www.espressomyespresso.com

Although there are some who will tell you not to backflush Silvia, it even states that it should be done to Silvia on the 1st-Line website. All machines that have a 3-way mechanism need to be backflushed.

[HB]

I have a 2 year old Silvia, manufacturer says do not back flush. Dan says "no problem".

To elaborate a bit, the strain on the system while backflushing is no greater than pulling a ristretto. It would be silly to claim that pulling a ristretto could potentially "harm" little Miss Silvia. More than likely the manufacturer is concerned that some fool will let the pump run 10 minutes against a blind basket, so they cover themselves by saying "don't backflush, it will void the warranty."

I do not know what it is exactly, what does it accomplish and I assume there is apart you have to buy to do this? Thanks.

In a nutshell, at the end of a shot when you turn off the pump, a solenoid opens to allow the pressurized brewhead to evacuate water into the driptray (the famous "whoosh" sound). Some grounds and coffee oils are carried along with the water, eventually building up on the pathway and solenoid. If this buildup is left unchecked, the solenoid may fail to close properly.

Backflushing involves running the pump against a blind (no hole) basket, either with water or adding some espresso detergent (like Cafiza, PuroCaff, or JoeGlo). The detergent backflushes remove the oils and gunk that have built up along the pathway and the rest of the group surfaces behind the dispersion screen (e.g., the water jet breaker). Most recommend detergent backflushes every week or two (Espresso Machine Cleaning - Why, How, and When explains in detail). Brief water backflushes reduce buildup between detergent backflushes. I do a quick water backflush and "wiggle rinse" every session.

[Randy G.]

To elaborate a bit, the strain on the system while backflushing is no greater than pulling a ristretto. It would be silly to claim that pulling a ristretto could potentially "harm" little Miss Silvia. More than likely the manufacturer is concerned that some fool will let the pump run 10 minutes against a blind basket, so they cover themselves by saying "don't backflush, it will void the warranty."

There is a bit more to it than that (IMO). When the blind portafilter is full of water and you turn the machine off and then on again, there is virtually no air in the system and what is called water hammer is created (at least that's what we called it when I was a firefigher). We learned that a hydrant should be closed slowly, otherwise you can actually send a shock through the water system that can blow pipes in the system or even in neighboring homes. You get the same thing in your home when the dishwasher or washing machine turns the water valve off and you can hear the big knock in the pipes.

After the first cycle of having the pump on, water has filled the espresso machine's system and since water does not compress the pressure builds very rapidly when the pump is subsequently reactivated. Depending on the OPV's ability to handle this rapid ramp up in pressure dictates the level of shock the system takes. You can actually hear the difference in the way the machine operates when this happens.

Still, if something bad happens when backflushing it was (IMO) about to happen soon anyway. Possibilities include:
-blown boiler seal (easily replaced)
-blown hose " "
-hose pops off " "
-pump fails " "

After two years of use, the OP should also disassemble the 3-way and clean it off the machine as well.

For a data point, my 6.5 year old Silvia has been backflushed numerous times and has never had any seal other than the steam valve O-rings and brewhead gasket replaced which are normal service items.

[HB]

After the first cycle of having the pump on, water has filled the espresso machine's system and since water does not compress the pressure builds very rapidly when the pump is subsequently reactivated. Depending on the OPV's ability to handle this rapid ramp up in pressure dictates the level of shock the system takes. You can actually hear the difference in the way the machine operates when this happens.

"Rapid" ramp up in pressure? A vibe pump takes several seconds to build to full pressure, unlike your analogy to fire hydrants and dishwaters supplied by mains line pressure. Assuming a modicum of common sense, I don't believe there's a risk of breaking anything.

[Randy G.]

"Rapid" ramp up in pressure? A vibe pump takes several seconds to build to full pressure, unlike your analogy to fire hydrants and dishwaters supplied by mains line pressure. Assuming a modicum of common sense, I don't believe there's a risk of breaking anything.

"Rapid" is a relative term, and the more accurate way for me to have said that would have been, "more rapidly than usual." Since there is no gicleur or any sort of device to create a flow restriction in Silvia, the PF gets as much as the pump can deliver as soon as it can deliver it. It is easily demonstrated by how slowly the pump ramps up the first time with the portafilter sans water, and how quickly the pressure ramps up once the blind filter is filled with water.

But if you read (have read...?) my "lesson" on backflushing on my website you will see (have seen) that I agree with you totally that there is no reasonable amount risk of associated with backflushing.