DE question re light versus heavy backwash

[cs7]

I've looked through a number of DE posts on TFP but don't see this particular question addressed - apologies if it is duplicative. There are lots of posts about how much DE to put back in after a backwash, how much weight is in the blue DE scoop, but i've not found anything addressing how light versus heavy backwashing.

For context, the pool system had an old sand filter when we bought this house three years and I got a new DE filter this spring, so I'm still learning how to do this. The pressure hadn't gone up much but I decided to do a light backwash anyway because it had been several months and I was doing an extra thorough cleaning of everything else. So I ran it for about 90 seconds, but by then the window was perfectly clear and so I rinsed for 30 seconds and then that was it.

I have seen instructions to backwash a DE filter for 2-3 minutes, rinse and then repeat those steps 3 or 4 times but that clearly wasn't necessary here. i have also seen warnings on TFP that putting in excessive DE, in addition to being wasteful, can mess up your filter. Is there anywhere a chart or analysis of how to account for how much DE you lose per minute of backwash/filtering, for the purpose of adjusting how much to replenish afterward?

For now I put six blue scoops in. I have a 60 sq ft vertical Jandy. and the pressure now seems a little low. Is that the answer? Put in scoops until you get back to the right pressure?

Thanks for any advice. I'm enjoying figuring all this out and appreciate TFP and its community; recently took the plunge to buy a TFP chemistry kit and have started doing my own testing.

 

[Jimrahbe]

7,

There is really no such thing as a 'light' backwash..

When you initially backwash, you will get most all of the DE that is every coming out.

Subsequent backwashing might remove a small amount of DE, but not much.

After you have backwashed two or three times, you really need to open the filter, remove the grids and clean them individually. Then reassembly and add the DE for a new filter.

Thanks,

Jim R.

 

[cs7]

I see, so when the water is cloudy and then goes clear the cloudiness is all the DE leaving the filter and it needs a full replenishment every time. Thank you!

 

[Jimrahbe]

so when the water is cloudy and then goes clear the cloudiness is all the DE leaving the filter and it needs a full replenishment every time

7,

Sorry that is not what I was trying to say..

When you backwash you remove about 80 or 90% of the dirty DE.. But, as time goes on, more and more of the DE tends to stay in the filters after a backwash.. After a few backwashes, it just makes sense to open the filter and clean it.

If the DE filter has just been opened and cleaned you add 100% of the DE the manual says to add.

After a backwash you just add about 80%.

Thanks,

Jim R.

 

[trivetman]

Cs - backwashing never gets rid of all the DE. I only backwash at the end of the season, immediately prior to opening the filter and cleaning it out properly. No matter how long i backwash or do rinse intervals between backwashing, theres always a some amount of DE left in the filter when i open it up.

Like Jim said, add 80% after a backwash. It doesn’t need to be precise. But more importantly, don’t backwash more than a few times without opening it up and cleaning it out properly

 

[cs7]

Got it, thanks to you both.