I have a question about how much DE to add to an old 36 sq-ft Nautilus filter. My ancient owners manual states 9 quarts of DE, and since 48 oz (volume) of DE is roughly a pound that adds up to 6 lbs. Funny thing is I found a more recent owners manual for a stainless steel NS36 online and that recommends only 3.6 lbs (judging from the schematics it is basically the same filter). I recently manually cleaned the grids and I can tell you that there was a ton of DE at the bottom of the tank, which leads me to believe the 9qts/6lbs is over kill. This time around I back-washed and added about 2.9lbs or roughly 80% of the 3.6lbs recommended in the newer owners manual. I'm just looking for the suggestion from some of the DE filter gurus around here as to what amount works well for you. Thanks.
DE Amount Old SS NS36 Nautilus
- Thread starter uloset
- Start date
- Jul 3, 2013
- 9,028
- Pool Size
- 15000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool SJ-40
I don't have a DE filter but I would go with the new filter recommendation and that would confirm what you are seeing about the DE setting in the bottom.. should save a pretty penny on DE now 
uloset
I have the same Nautilus Filter (NS 36) with a Pentair 36 Sq Ft Grid Assembly 59023500 .
I've been using the following D.E. charging amounts for several years:
With a new or cleaned (removed & cleaned) Grid Assembly, I charge with 3.6 Lbs (same as recommended by the Nautilus NS 36 manual and the template attached to the actual filter tank).
I use a "Leslie's Pool" light blue D.E. scoop which = approx .5 Lbs D.E. It's actually = 5 Sq Ft of D.E. coverage but that's close enough to consider the scoop = .5 Lbs.
So for a new (or removed/cleaned) Grid Assembly, I use 7 D.E. scoops.
When I backwash, I charge with 6 scoops which is = 80% of a full charge. That's recommended since a backwash won't remove all of the old D.E. from the filter.
That's = to 6 D.E. scoops.
Using the above charging methods, here's my filter backwash history for the past couple of years, since switching to TFP methods (Bleach/CYA ratio dosing)
05/15/14 Backwashed. This was the last Backwash done before switching to TFP methods. Prior to this, I usually had to backwash every 3-5 weeks, sometimes sooner.
11/07/14 Backwashed. 6 D.E. scoops Duration from last BW 25 weeks ~6 mo
02/17/15 Backwashed. 6 D.E. scoops Duration from last BW 15 weeks ~3.5 mo
06/01/15 Backwashed. 6 D.E. scoops Duration from last BW 15 weeks ~3.5 mo
11/23/15 Backwashed. 6 D.E. scoops Duration from last BW 25 weeks ~6 mo
04/18/16 Backwashed. 6 D.E. scoops Duration from last BW 21 weeks ~5 mo
I last replaced (or pulled the assy for complete cleaning) on 09/18/13
I backwash using 10 BW/Rinse cycles with my Multiport Valve. I think this is the reason I haven't had to pull the Grids sooner since I'm removing almost all of the D.E. in the Grids with multiple BW/Rinse cycles.
My "starting/best case" PSI (right after BW and before charging with D.E.) is about the same as with a completely new Grid Assembly.
I have the same Nautilus Filter (NS 36) with a Pentair 36 Sq Ft Grid Assembly 59023500 .
I've been using the following D.E. charging amounts for several years:
With a new or cleaned (removed & cleaned) Grid Assembly, I charge with 3.6 Lbs (same as recommended by the Nautilus NS 36 manual and the template attached to the actual filter tank).
I use a "Leslie's Pool" light blue D.E. scoop which = approx .5 Lbs D.E. It's actually = 5 Sq Ft of D.E. coverage but that's close enough to consider the scoop = .5 Lbs.
So for a new (or removed/cleaned) Grid Assembly, I use 7 D.E. scoops.
When I backwash, I charge with 6 scoops which is = 80% of a full charge. That's recommended since a backwash won't remove all of the old D.E. from the filter.
That's = to 6 D.E. scoops.
Using the above charging methods, here's my filter backwash history for the past couple of years, since switching to TFP methods (Bleach/CYA ratio dosing)
05/15/14 Backwashed. This was the last Backwash done before switching to TFP methods. Prior to this, I usually had to backwash every 3-5 weeks, sometimes sooner.
11/07/14 Backwashed. 6 D.E. scoops Duration from last BW 25 weeks ~6 mo
02/17/15 Backwashed. 6 D.E. scoops Duration from last BW 15 weeks ~3.5 mo
06/01/15 Backwashed. 6 D.E. scoops Duration from last BW 15 weeks ~3.5 mo
11/23/15 Backwashed. 6 D.E. scoops Duration from last BW 25 weeks ~6 mo
04/18/16 Backwashed. 6 D.E. scoops Duration from last BW 21 weeks ~5 mo
I last replaced (or pulled the assy for complete cleaning) on 09/18/13
I backwash using 10 BW/Rinse cycles with my Multiport Valve. I think this is the reason I haven't had to pull the Grids sooner since I'm removing almost all of the D.E. in the Grids with multiple BW/Rinse cycles.
My "starting/best case" PSI (right after BW and before charging with D.E.) is about the same as with a completely new Grid Assembly.
Sorry for the delay I was wrapped up in a wall paper removing project over the weekend (tons-o-fun). Thanks for the the replies especial Scoop, your in-depth post has all the info I could have ever asked for. I remember when I bought the house that the filter was able to clear the pool up from a swamp to crystal clear within in a day. Over the last few years even if I opened to a relatively clear pool "mesh cover" it still seemed to take forever to totally clear it up, even after manually cleaning the grids. Now thinking back on it I originally as going by the DE bags recommendations, which was far less than the manual which I found in the house much later.
I am happy to report that over the last few days the pool went from cleanish to crystal clear and that is with around 8 hours of total run time. Like you Scoop I also do a very thorough backwash/rinse cycle, but with the huge amount of DE I was using after a few years there must have been a few lbs of DE caked between the grids and even more on the bottom of the tank. Now using this lesser amount I wonder how much cleaner the grids will look after a season. Thanks again for all the info.
I am happy to report that over the last few days the pool went from cleanish to crystal clear and that is with around 8 hours of total run time. Like you Scoop I also do a very thorough backwash/rinse cycle, but with the huge amount of DE I was using after a few years there must have been a few lbs of DE caked between the grids and even more on the bottom of the tank. Now using this lesser amount I wonder how much cleaner the grids will look after a season. Thanks again for all the info.