First encounter with DE Filter

Hello All,

I'm so glad this site is back up just in time for pool season, I don't know what I would have done without it. I have just inherited an in-ground pool, and the filter that was left to me is a FNS Plus Vertical Grid DE 36sq ft filter. I used to have a sand filter for another pool in an old house, but I have never dealt with a DE filter before. It seems that it was cleaned last year before the pool store closed it. Any suggestions or tips on what I need to do to start it back up would be greatly appreciated. From reading other posts I've learned that it's good to mix the DE powder with some water before pouring into the skimmer. My main concern is actually how to just get the filter running. Is it as simple as just putting the lid and the clamp on, and starting it? Should I add water to the filter first? Thanks in advance for all the help..

Lost in DE land....

I'm not familiar with this particular filter. You should read the manual for directions on assembling and start up. If you don't have a manual, try this link:http://www.pentairpool.com/owners_ma...s/fns_plus.pdf
I usually put the required amount of DE in a 5 gallon bucket 3/4 full of pool water, mix it up with hands, then add to the skimmer by pouring slowly & steadily while the pump is running.

After getting the DE and any other needed materials to start the pool up (o-rings, gaskets, plugs, chlorine source, etc) and removing any winter plugs and reinstalling any pieces removed for the winter, you start up the pump and filter pretty much like any other pump and filter.

Prime the pump! It's been dry since the fall. Make sure there's enough water in the pool to get into the pipes and skimmers so the pump isn't sucking air.

Set the valving (if needed) to 'Normal' operating mode, where the water comes from the pool, into the pump, into the filter, and back to the pool. Then just add the DE into a skimmer and let it get sucked into the filter. It will coat the mesh elements in the filter and you are then good to go.

Some folks make a slurry with the DE and some water in a 5 gallon bucket first,others just add it to the skimmer. Do -NOT- breathe in the DE dust.

Mike was right, but be sure that you use the 'air relief screw' on the top of the filter to vent out the air before adding the D.E. If you don't get ~all the air out first, the dry parts of the filter grid, or fingers, won't get the coating of DE they need.
As a side note, the DE 'slurry' is only needed when you only have 1 suction source, with more, the action of two sources removes this need.

Thank you for the replies. Let me see if I have got it right.

After I hook up all the pipes, and make sure the water level is high enough in the pool so that the filter doesn't run dry. I will turn on the pump/filter. After a few minutes I will let the air out with the 'air relief screw' and the pour the DE into the skimmer. Do I need to do anything else after that, other then put in other chemicals (i.e., bleach, borox) ?

Quote:

---

Originally Posted by waste

As a side note, the DE 'slurry' is only needed when you only have 1 suction source, with more, the action of two sources removes this need.

---

waste, could you explain this a little further? I have 2 skimmers but close the unused one when I'd adding DE. I haven't intentionally openend any other input source when doing this.

A DE filter is similar in operation to a sand filter, except that instead of semi-permanent sand as the filter media a DE filter uses replaceable DE as the filter media.

When you backwash a sand filter, you are running the water 'backwards' through the filter and pushing the gunk out of the sand and out the backwash pipe/port. The sand stays in the filter (hopefully).

When you backwash a DE filter, you are running the water 'backwards' through the filter and flushing the gunk and the dirty DE out the backwash pipe/port. After you are done backwashing and reset the valving for 'normal' operation, you then have to add new DE to the filter.

If you're OK with the start-up of your old sand filter, you should be OK with starting up the new DE system. Just remember that the filter isn't filtering until after you put the DE in.

On my DE filter, if the filter is not filled with water, I'll open the air bleeder valve manually when I start the pump until I get some water into the top of the filter tank and out the bleeder valve. I'll close the bleeder valve at that point, let it run for a little bit (30 seconds, a minute, whatever) and then reopen the valve again and 'burp' out a little more air. After I have water flowing 'normally' through the pump/filter/pipes for a few minutes, then I add the DE into a skimmer.

Do you need anything else? Remember that the DE is just the filter media, the rest of the pool chemistry still has to be taken care of as usual. Bleach, borax, baking soda, acid, whatever.

Thanks for all the help. I successfully opened the pool today. My psi on the filter is currently at 4. Is that normal, or does it seem a bit low? I've got plenty of water in the pool, the return pressure seems normal. I've already added about 7 cups of DE "slurry" to the skimmer.

7 cups of DE, as in seven 8-ounce measuring cups??? Way too little DE.

There should be a label on the filter saying how much DE to use. A 36 ft2 DE filter usually should take about 3.6 pounds of DE. An empty 'pound' coffee can will hold about 1/2 pound of DE powder, so you'd need 7 cans full of DE to get your 3.5 pounds of DE (close enough to 3.6 pounds).

As to the pressure, maybe your pressure gauge is NG and needs to be replaced. Or you don't have to valving set properly and you are starving the pump of water and hence have a very low pressure. Or you have a suction-side air leak and hence have low pressure. It could be many things, or maybe that is just the pressure that your clean filter runs at.

1. Dont guess how much DE to use. The DE box will tell you exactly how much to use. Just put that amount in a bucket. Add some water to make a slurry and dump it in the skimmer. The slurry will coat the filter. Once you do this and let it run awhile, you can shut the pump off, remove the filter cover and visually observe that the DE is coating the filter like white mud. There shouldnt be any screen visible. Its really pretty simply and fail proof. You wont screw it up.

2. I do not rely on the pressure guage on the filter to tell me when to change the DE. I have found that my filter can be totally clogged and the pressure guage doesnt move at all. (And I am an oilfield engineer and I replaced my cheap pressure guage with a high quaility industrial brass one -- its not the guage.) I have found that when my filter is new, the return line to the pool is very strong -- like a jacuzzi jet and my vacuum works great. When my vacuum doesnt pick up or the kids complain that the return jet in the pool is weak, I know its time to change the DE. I have found that changing the DE every month works very well. Some people say that you can let it go almost a season, but I like strong filtration. Its your preference.

Quote:

---

Originally Posted by Lenny

waste, could you explain this a little further? I have 2 skimmers but close the unused one when I'd adding DE. I haven't intentionally openend any other input source when doing this.

---

Lenny, sorry about the delay! I actually answered you last week but my wife came in and used the computer while I was doing it ( I thought I had hit "post", but apparently hadn't - again, sorry).
With 2 suctions going, you have a plug of DE laden water comming through 1 and an equal amount of non-DE water comming through the other. This ~ equates to doing the slurry (DE mixed with water joining with plain water). I know for a fact that this evenly coats the grids, or fingers, because I've had reason to open a number of them almost as soon as the DE has been added and they have always had a good, even coating.

Thanks Waste! That makes sense.

I'm running a 36sqft DE filter also- if memory serves me correctly (and it's getting worse every day) I used 36 cups of DE to replenish my filter. Check the instructions on the bag. I wouldn't recommend mixing it with your hands - get a heavy duty yard stick or something. I also use 2 buckets and mix it half and half, that's a lot of DE to mix in one bucket and it makes it easier to dump into the skimmer, especially if you're 5'3 like I am. Stir it quick right before putting it in- it settles to the bottom of the bucket quickly. Rinse your buckets out good - and mark them for DE USE ONLY!!

ALSO- lube any O rings, my filter comes apart in half and there's one big one all the way around it.

My DE filter has been a life-saver with our iron issue here in Nebraska. The pool store lady had a fit and told me to not use a DE filter with our iron problems; when in fact that's even more reason to use one! I'm not putting down sand filters, but I keep reading posts about people using sand filters and adding DE powder to them, or Zeolite (sp?)... to get similar results of a DE filter; WHY NOT JUST GET A DE FILTER???