DE backwash question

[Serious1]

This is our first year with a pool. The PB hasn't pool schooled us and has been dropping by once in a while to check on things. They normally backwash and throw 5 pucks in the skimmers. I wait till they leave and pull the pucks out. My FC is 9.5 with the swg at 10% so I'm trying to find the sweet spot of getting FC down a tad before I add more stabilizer to continue to get CYA up. At 10% swg setting (running 24/7) it climbs about 0.5 FC overnight.

FC 9.5 (was 9.0 last night)
CC 0
PH 7.6 (I add a quart of MA weekly to keep this down)
TA 170 (was 230 before 3 weeks of adding MA)
CH 230
CYA 60 (was 0, shooting for 70 now, but I find it takes at least a week to register after I put it in)
salt 3000 (that is a reading from the hayward, I don't have test strips for this yet)

Here's my question:
I read thru the use and care for DE filters but i'm confused on the instructions. It says "pretty much the same as bump"....does that include opening the air valve for 5 seconds?

Also, I plan on adding 2 or 3 scoops of DE after backwashing, but the PB said to add 5 lbs; as with the pucks, i'm throwing out that advice. I have the proper scoop and have a kitchen scale so that I can be precise...or maybe because I've never actually used it for anything in the kitchen so figured I should get some use out of it.

 

[JoyfulNoise]

What size DE filter do you have?

The recommendation is this - you only backwash your filter when the pressure rises 25% over clean pressure. So if your pool started out with 10psi clean pressure when it was first started, then you don't backwash until your gauge reads 12.5psi.

When you do backwash, add less than half the recommended amount of DE for a full charge. Backwashing rarely removes more than half the DE.

My DE filter is very oversized relative to my pool so I no longer backwash anymore. I simply tear down my filter twice per year and do a full clean. I use less DE that way and it puts less stress on my filter. Depending on how large your DE filter is and your debris load, you may be able to do that as well.

Add a polypropylene hair net to your skimmer baskets -

Disposable Hair Net, Spun-Bonded Polypropylene, White, 100 per Bag: Science Lab Hairnets: Amazon.com: Industrial Scientific

They help to keep the heavy debris out of your filter.

 

[Jimrahbe]

There is no reason to add pucks to the skimmer, or anywhere else, if you have a SWG. Good job on taking them out.

As far as your DE filter.. there is no reason to backwash it unless it needs it. At the top of the filter is a PSI gage. When clean, the pressure will read say 10 PSI (Yours may be a little different). As you use the pool, this pressure will increase as the filter gets dirty. When the pressure increases to a specific level you then backwash. I believe that the TFP rule is an increase of about 25%.

After you backwash you need to add about 80% of the amount of DE that the filter normally holds. This depends on the size of your filter, so unless you know the size of your filter you can't know the correct amount of DE to add.

Unless this pool is very new, or you have a variable speed pump, there is no reason to run your pump 24/7. Reducing your run pump run time would also reduce the amount of FC your SWG is making.

Jim R.

 

[Serious1]

thanks for the replies.

original question: do i need to do anything with the air valve before/after backwashing?

PSI is normally 9, I backwash at 12. Filter is 37.5, so 3.7 lbs is the new/cleaned amt, 2.96 would be 80% of that. I do use skimmer nets when I can check them often. I would never leave them with the amt of cotton we have flying around here.

Our pool is new, this is the first season and we're fine running the pump 24/7.

 

[BuckeyeChris]

IIRC my instructions said 70% of DE that you'd add at a clean start up. I'd add 50% and then see where your PSI is, then add scoop by scoop until the PSI gets back to your start up PSI.

Or...just do a full disassemble once a year. I don't have a nice place to backwash the DE to.

 

[Serious1]

but my question is what is the air valve for?

 

[Jimrahbe]

The valve at the top of the filter is to let out air that can get trapped in there. Anytime the water is allowed to drain out of the filter, like when you disassemble and clean it, or sometimes when you remove the pump lid, air can get inside the filter. When the pump is turned back on you should open the valve to purge the air. Just open the valve until a stream of water comes out and then close it.

Jim R.

 

[Serious1]

ok, makes sense. Thanks Jim!