Back washing pool filters

[Foreverlookin]

I have a Pentair 4000 series pool filter and was back washing whenever the water stopped going over the spillway on the hot tub back into the pool. I was talking to a pool service guy and he said it's not a good idea to back wash these filters as it shortens their life span....found that weird until he said he could clean it for $75 it all added up after that he was drumming up business I think.

Typically when I back wash I run it to drain for 30 seconds and then mix up 6 scoops of diatomaceous earth in water and pour it into the strainer basket.

Am I doing something wrong?

Thanks

 

[Richard320]

He's full of it. Or maybe halfway full.

My experience is that they don't backwash well, and 30 seconds is not enough time.

My routine, which I only have to do about every nine months:
Backwash until the water looks clear coming out the hose.
Shut off pump.
Open air bleed with backwash open until it drains.
Close backwash valve - and all you Helpful Henrys should know the backwash is integral and underneath on these filters. Close air bleed.
Remove clamp.
Turn on pump just long enough for air pressure to pop the lid loose. Set the lid aside. Avoid touching it with bare arms. Ask me how I know.
Open backwash valve.
Blast the screens with a hose nozzle. Huge amounts of sludge will end up in the backwash hose. You might need to loosen the wingnut and the upper clamp to tilt the screens for easier access. You can also remove them, but I don't find it necessary.
Reassemble it all. Getting the lid on is the hardest part. Might need extra hands and multiple pliers.
Turn on the pump and backwash until the water is clear.
Close backwash valve. Remove hose. Start filter and recharge with DE or cellulose. Watch for drips out the waste line. The valve may need open and close a few times to get things to seat right. Run it a few minutes and bleed air out the top.

http://www.pentairpool.com/pdfs/SMBW4000SeriesFilter.pdf is the manual./ If you're unsure of the filter model, measure the screen heights while it's open. Page 10 of that manual will help you figure out the exact filter by grid size.

Also, set the valves in the usual position and note the clean pressure. When it rises 25%, backwash again. Say it normally runs 12 psi clean, backwash at 15.

It almost takes as long to type this as to do it.

Some photos of mine all opened up I'm tempted

 

[JamesW]

It would not be safe to pop the lid with air pressure. The lid can come off quite violently. Most filters have stickers that explicitly warn about this.

THIS FILTER OPERATES UNDER HIGH PRESSURE. WHEN ANY PART OF THE CIRCULATING SYSTEM, e.g.,CLAMP, PUMP, FILTER, VALVE(S), ETC. IS SERVICED, AIR CAN ENTER THE SYSTEM AND BECOME PRESSURIZED. PRESSURIZED AIR CAN CAUSE THE LID TO BE BLOWN OFF WHICH CAN RESULT IN SEVERE INJURY, DEATH, OR PROPERTY DAMAGE. TO AVOID THIS POTENTIAL HAZARD, FOLLOW THESE INSTRUCTIONS. (From the manual)