Improving the Filtration of a Sand Filter?

[vaughanwilliams]

We tried something on a pool filter which I would appreciate your comments on.

The problem was very fine dust entering the pool via the inlets during vacuuming. If we vacced to waste, there was no problem. Vac to filter, the dust started after a few seconds.

We tried ripping up paper kitchen roll into fine pieces about the size of a postage stamp and dropping them into the pool near the suction port. (Overflow pool). The pieces of paper were drawn into the suction line and were macerated by the pump (minus the strainer basket) and this mush was then trapped in the filter, covering the sand (so went the theory). This should have added an extra fine layer of filtration which would have been flushed out with the crud on backwashing.

Result? Not a darn bit better, the dust still came through.

Any ideas?

 

[SPP]

Hello again Vaugh,

Before my sand filter gets changed to zeolite I had the same problem, but not with dust, its with fine dirt when vacuuming and set to filter. So I install a cartridge filter downstream of my sand filter. The logic to me is simple. Sand is a rough filtration media, 50 micron is what filter manufacturer usually stated...so when I vacuum and start seeing that fine dirt coming out, that means is smaller than what my filter is able to filter.

I knew of this because I algaecide the pool, so the algae is visible, very very fine green like dust. I then realized its too small to filter. I do not know if ur problem is from broken lateral or something else but as far as filtration is concerned 50 micron is too rough, too big for me. With the cartridge downstream of the sand, I am OK. In fact my back up pump on trolley only use a cartridge and I sometime uses that for vacuum...its good.

My pool gets vacuumed nearly everyday. The cost of the cartridge filter gets recovered fast, since my vaccuming takes like 20 minute at least. My pool boy really take his time slowly. I also gets better clarity with 10 micron cartridge. Finer particle I can trap.

If your filter has no fault, I can only think that you are seeing the very dust you are vacuuming. Whatever dust you vacuum is not visible on pool bottom but maybe at the pool inlet nozzle it is clearly visible because its concentrated.

People here put some DE powder to make the sand a better filter. You read that at the other post SAND FILTER.
Another possibility is your pump too big for the sand filter.
Experts here will advice you soon for sure.

Good luck....

 

[New2Me]

I don't vac much myself, 'cause I'm lazy, so I drop in an Aquabot and let it work. When I don't want to do the whole pool(just spot clean) or I want to add water, or it's too cold for the 'bot(opening) I'll use a Black Magic water-venturi vac with an aquabot bag on it. The bags are a fine mesh fabric, here's Aqua Products filtration claim-

Self Contained, 19-quart. capacity; Large leaves to fine particles down to 2 Microns

which I got here http://www.aquaproducts.com/ap/products/aquabot_turbo.php
You can get replacement bags for ~$50US. I've thought of getting an inline leaf cannister for the vac for the same purpose, but haven't yet(I'm lazy.) You could probably put a bag in one of those. I don't know how fine the skimmer sock filters are, but those would work too. I've also heard that too frequent backwashing of a sand filter reduces its effectiveness, it filters better when its dirty, you don't want to backwash it right before you vac. Some people here have good results using DE on top of sand, or using zeobrite. Lots of options, best of Luck!

 

[New2Me]

Here's that inline filter cannister-
http://www.pentairpool.com/products/products3.php?id=85
Other manufacturers have similar products.

 

[JasonLion]

Either the dust is extremely fine or there is something wrong with the filter. Dust fine enough to go through a sand filter is usually small enough that it is difficult to see, which doesn't seem to fit your description. More likely the sand has become channelized, or something more serious is wrong with the filter.

 

[searayboater]

This is what you need!

 

[vaughanwilliams]

I've heard about slime bags and would like to try one. Unfortunately, they aren't available in Cyprus, as far as I know.

 

[SPP]

Aha...Slime Bag...see my signature
Jason showed me that product too and I bought it.

That bag will surely catch whatever you are vacuuming, provided your plumbing can have fitting for that. It filters from inside the bag to outside, opposite to normal filter. Contact them and they can send you by post office...cheap.

However do remember one thing.....after long use, there will be some very very vert fine greenish dust ( most likely algae ) that will stick outside the bag. Pull the bag slowly out of the water you will see the water around the bag will turn mild green.. but it is so fine...when you stir the water around it will simply dissapear. Whether those are baby algae...I don't know. Whatever it is I am happy if I can catch even things I do not see in my water, the end result will be always better clarity.

Do a search on slime bag, I posted my test result.

Look at photos below.
This is how my friend whom I also bought slime bag for, use it. I set it up as such.
He has a robot that pumps out water pressure, so when not in use I can use the robot dedicated pump to become a filter pump. As I said, the slime bag filters from inside to outside. You are looking at the Jumbo Slime bag, inside it there is another sock version, the biggest sock version...I can't remember the model. Regardless that it is a 2 element set up, you will still see the green fine diust I mentioned, when you move the filter.

The locking mechanism on photo 2 is called Cam-Lock. Its industrial fittings, easy to use and heavy duty. If you buy this fitting, do not use the aluminum one, it will corrode in no time. Choose stainless steel or maybe the plastic version if they have. No pool store sell this coupling, go to ship supply store or industrial water fittings.

The PVC pipes/manifold, I make myself.
Good luck

 

[MEvan]

Im not sure what people on this site think about alum flock, but it works great as a sand filter aid. It costs 13.99 for a 4 lb bucket where I work and you go through it slowly. Just add it through the skimmer as per directions and it creates a gel over the top of your sand which catches finer particles. If you look at instructions for layering large sand filter media when installing, many show this as the top layer. I prefer this over DE. This product can also be used as a water clarifier if diluted and added directly. I just did an internet search and it was harder to find than I thought http://www.aboveground-swimming-pools.c ... _lbs..html
Give it a try and tell me what you think. Does anyone else have an oppinion on flock?

 

[duraleigh]

Matthew,

That's very interesting and I'm not sure floc has been mentioned on this forum as a filter aid.

I assume it backwashes out pretty easily.

What if you put in too much (someone surely will)....would removal be difficult?

How do you know how much is right? psi increase?

Do you think it may have advantages over adding DE?

 

[SPP]

MEvan,

You are in luck. I just use this floc yesterday on my friend's pool. It is called PAC Poly Aluminium Chloride.
I learn this from the pool supply shop friend. This is a cheap industrial chemical which if I am not wrong the pool boy paid only US$0.50 per 2.2lbs/kg.

I too searched TFP but could not get PAC information.

I can not find its application dose on the internet, I mean as a floc agent. I wanted to know if it will "poison" the pool water.
This is very populer use with waste treatment people, so they said.

I personally did not see the stuff. I just told the pool boy to buy and broadcast 4.4 lbs in a 60K gallon pool. The advice from the pool store on a pool that size is no more than 4.4 lbs... , I think must ask water treatment people for proper dosage.

The drill for local pool builder here is and I believe they did that to my pool when I first fill up :
- Cal-Hypo
- Copper Sulphate
- PAC

Then the green swampy thing happened...filter filter filter till clear water.

The pool boy did vacuum the PAC residue this morning after about 20 hours of application. The sand filter ( zelbrite ) and cartidge showed 1 psi increase in pressure, but the pool was rather green with algae too. That's why I floc with PAC

My pool supply friend said always watch the pressure gauge because with PAC, the filters usually clog fast. My back up pump on trolley that I sent there to assist, it has cartridge filter only and Slime Bag downstream...both did clog. That slime bag on the photo, also clogged.

I would imagine if you place the PAC in the sand filter, it may actually floc algae but given the water flow in the filter itself, I don't know if it can do that as effectively as when you broadcast it in a pool.

I have not seen the pool. The pool boy said that the pool is cloudy like heck after the PAC... . I guess the PAC worked well as floc then....that's what it is suppose to do anyway.

 

[MEvan]

I will have to look into whether or not that really cheap stuff is the same as alum flock. Ours, when used as a sand filter aid, is to be added at a rate of three ounces for every square foot of filter area. I prefer it over DE, I think that DE is just a total mess and hate using it when I dont have to. I also think its results in sand filters are unpredictable. Its a great product to have on hand. Liquid clarifiers cost a lot more and you get less. I have one pool I do weekly service on that is around 35,000k. They get a lot of fine dirt and have a continual problem with very slight cloudyness. Ever since I began using flock in their filter as directed, the problem has been completely solved.

 

[duraleigh]

Hi, Matt,

I'm interested in trying this. Can you tell us what brand you use?

Sand filters are not often rated in sq feet of filter area but I assume my 36" Triton would have 7 sq feet of exposed surface area...make sense?

Tell me if it backwashes easily.