Backflushing imparts no more stress on the pump than the typical shot.

You need to disassemble the grouphead as previously advised - takes all of 5 minutes including finding the screwdrivers or wrenches.

Thanks for the tips.

I read with interest the discussion on "backflushing" this morning and if I may add my own thoughts and IMHO.
It should be made clear that the cleaning that occurs, happens while the machine is in the "off" cycle. ie. 5 seconds "on" w/ soap and then 20 seconds "off" while all the soapy, oily crud is discharged out the 3 rd port of the 3 way valve.
When this soapy discharge comes out white, you're done with the soap. If, after several cycles of backflushing, discharge water does not come out clear, do the soap solution again, add more soap. If your soap solution doesn't have a strong foaming action, IMHO you need a different detergent. It is this foaming activity that scrubs out the inside of the group head.
How often to backflush, depends on how well you backflush and how many shots you make between backflushing.

Not all screens are designed to come out for cleaning. Nor is this necessary for good cleaning. Every time you take something apart, you risk not being able to put it back together correctly. Parts get lost, screws can get cross-threaded. This happens often enough that I often am asked for extras while servicing equipment. And I have on more than one occasion had to install new threads into someone's group head.
Another "hazzard" of backflushing happens at the end of the shift when people want to go home and haven't rinsed the soap out of the group head adequately. The soap dries in the group head and the valve is seized.

I would think that any machine with a 3 way valve the manufacturer recommends NOT backflushing because of "inadequate water lines" would be very marginal brewing regular shots, as the pressure difference is minimal and after all, the 3 port is vented to atmospheric pressure.
However, as finicky as people seem to be about keeping their machines clean, I can imagine the manufacturer would be very tired of "warrenttee work" on group heads seized up with soap.

Just my .02

Norm

I had a Faema Family for 14 yrs or so, and I never backflushed it. It never failed in all those years, and when it finally did, the problem had nothing to do with dirty lines etc. but with a leaky valve. Only when I was looking for a new machine, I discovered this odd ritual called backflushing. I'm not a heavy user - maybe 20-25 cups in a normal week - but still, 14 yrs is a long time.

I descaled my Family about 4 times per year and I removed the shower screen regularly and cleaned it. The other thing I did was run water through the portafilter (filter inserted) to heat it up. But that was it.

The Family is a SB, maybe that makes a difference?

I used to do plain-water backflushes after each session on my GS/3, and detergent backflushes once a week. Now I just do the detergent backflushes once a week. I haven't detected any difference in flavor or machine operation.

My theory on this is that if coffee oils and particles that are smaller than the holes in the screen are baking onto the small inner diameter of the feed tube (TL-30 in the GS/3), then it takes more than plain hot water to wash them off the inside of the copper tube and onto the puck. And even if they get there, how much of that stuff is there and how much can get past the top of the puck and really affect the drink?

Now, one thing I've noticed is that over a week's time more fine particles accumulate on the back of the screen when I pull larger doses than happens with smaller doses. Since I tend towards smaller doses in the 14g-16g range, there's not a lot of particle accumulation on the back of the screen between weekly backflushes and probably less coffee debris in the tube as well.

As for technique, I prefer to remove the screen and scrub it and the dispersion block (not easily removable) with a Pallo brush and hot water. Coffee oils and small particles of coffee accumulate on the back of the screen and sometimes on the dispersion block, and I see no point in flushing that stuff through the feed tube and 3-way valve. I drop the screen, portafilter and any baskets I've been using into a container with about 600ml of water and two Tbs of espresso machine detergent. I let them soak, with occaisional agitation, for about 30 minutes, then rinse thoroughly under very hot water.

At the same time, I do a 1/4 tsp detergent backflush without the screen. I mix a little hot water with the detergent to pre-dissolve it before locking in the PF. I pulse the machine twice, then let the soapy water sit in the tube for about 15 minutes. Then I put another 1/4 tsp of detergent in the blind filter and run the machine through its automatic cleaning cycle (15 timed backflush pulses.) Then I repeat the cycle twice with plain water to get the detergent out (total of 30 cycles.) I use Jo-Glo, which doesn't foam much. I think foam has little to do with it: the chemicals do the dissolving. At any rate, when I've compared the ability of a foaming detergent like Cafiza against Jo-Glo in getting visible coffee stains off the inside of a brew machine carafe, the Jo-Glo did a much better job.

I reassemble everything and then run the brew cycle into a measuring cup for the maximum 50 seconds to determine the flow rate (making sure the tiny gicleur isn't clogged.)

The best backflushing regime and procedure is the one that works best for your machine and your situation. As Dick outlined above, he found what works for him. It won't work for me. Why? With an E-61 group you cannot backflush without the screen in place because the group gasket comes out with the screen. Placing the gasket back into the group without the screen means you most likely will damage the gasket removing it to replace the screen. Even just once a month would cost around $50 a year in gaskets. Additionally, the internal parts of the E-61 do not seem to take kindly to detergent backflushing too often. Clean water backflushing after every session keeps my group very clean internally. Once or twice a year I take the group apart for an external cleaning and inspection. Very easy on the E-61, even after a beer.

So the bottom line is, find what works for you.

I backflush for about 10 seconds and then a few 3-4 second bursts with water only every day or two. I figured I'd use the detergent once every two weeks.