Filter Bag Backwash FAIL

[hyperionguy]

I decided to try what was suggested to me. Use the same filter bags folks are using to allegedly increase filtering capabilities. It seemed to make sense.

A sand filter goes down to typically 20-30 microns, right? Some folks (based on threads I've searched) seem to think that putting a 1-5 micron bag onto their return hose gives them DE-like filtering. I now seem to have evidence to refute what I already felt was BS.

If a 5 micron bag filters debris that passes through a 20-30 micron sand filter, then I should be golden if I use it to filter backwash water as I shoot it back into the pool.

I sealed off a Duda Diesel 5 micron 14" bag onto my return hose and pointed it back into the pool. I ran backwash for about 3-4 seconds without a problem. Then all of a sudden a brown cloud started coming out of the bag. No, it wasn't a leak in the seal. The cloud was evenly distributed out of the whole surface area of the bag.

Fortunately I yanked it out after about 3 seconds of cloud generation.

So I'm wondering what went wrong. Do the bags not really filter to 5 microns? Do they filter to 5 microns when the liquid passing through is either at gravity or slightly above and the flow from a pump is too much and the PSI pushed stuff out? Do I need to buy the much larger/longer bag to reduce PSI/sq-inch?

Based on the results... with higher volume pumps are people who think they are getting superior filtering really experiencing something that's all in their head?

Discuss....

 

[PridgNYC]

Why would you backwash back into the pool? Backwash washes out all the particles that were captured by the filter, typically to waste. If you sent all that bulk through to a microfine filter, you probably caused multiple failures in the micro mesh causing your 'cloud'. The original idea was to add the ultrafine filter to the return so it could filter out any ultra fine particles that were missed by your filter, however you decided, for some reason, to send everything captured by your filter through the bag since the last time you backwashed, it's no wonder it failed in rather dramatic fashion.

The method is to allow your sand filter to take care of the larger particles which will quickly clog the micron filter bag and allow the fine filter bag to capture any tiny particles that it missed, hence the reason for attaching it to the outflow after your filter has processed the water. By attaching it to the backflow hose (which is supposed to go to waste) you basically dumped every particle captured by your filter no matter what size it was, and yes it was the clogging of the bag with the larger particles and resulting psi increase that caused your filter bag to fail. I can tell just by the pictures that you dumped so much Crud into that bag that it basically developed thousands of tears to allow the water pressure through that it was no longer effective at filtering anything.

 

[jblizzle]

In theory it should have worked ... if cheifwej can backwash his DE filter back into the pool through a DE separator. Likely you just needed a bigger bag.

Still seems a bit silly to me

 

[hyperionguy]

There are many reasons to backwash back into the pool. If you research older threads you'll see it. What I'm trying to figure out is what the proper bag sq/ft relative to discharge rate should be. It'll work if it is setup properly. It's fairly simple mechanics if you have the right calculations, which I don't have.

If you look at raw diesel filtering under pressure, you'll see that it isn't like pre-filtered pool water wisping thorough with a few little particles being caught as you suggest. It's thick, heavy, pressurized fluid passing through the 5 micron filter. I would expect similar performance from pool water. I'm pretty sure that it is related more to the gph being shoved through rather than the total debris load being thrust at the filter.

The purpose for backwashing into the pool is related to smaller Intex pools where a proper backwash has a significant impact on water levels as well as dilution of salt, Ph, TA, and borates. Additionally, like many others my pool is in a smaller area (patio home) where blasting backwash into the yard wrecks everything. It is a problem that needs to be mitigated in an aggressive way.

 

[PridgNYC]

You'll need a much bigger bag considering how much gunk clogged that tiny bag. In theory it is doable, but not with that tiny filter. You need something that is big enough to handle all the large debris trapped by your sand filter and still have enough area left for effective filtration without clogging.

The comparison to diesel filtration doesn't make any sense as that uses metal mesh filters that are designed to handle the pressure. That bag isn't designed to handle the pressure of even mild clogging.

 

[duraleigh]

There are many reasons to backwash back into the pool.

Color me obtuse but I can't think of one.

Do you think you read about those bags on this forum?

 

[jblizzle]

I recall seeing this theorized somewhere on the forum ... not sure where though.

If it worked, I can see the benefit of not losing the salt, CYA, etc and not having to deal with a location for backwashing the water.

 

[hyperionguy]

The comparison to diesel filtration doesn't make any sense as that uses metal mesh filters that are designed to handle the pressure. That bag isn't designed to handle the pressure of even mild clogging.

Perhaps you are somewhat right in some respect, but the bags purchased are actual diesel filter bags designed and sold for use in the stainless steel pressurized filter tanks used for that purpose.

See polyester bag, 4" by 14" http://www.dudadiesel.com/search.php?query=+filter++bag&i=filterbags

Designed to fit housing size #4 stainless steel pressure tank at the bottom right of the same page.

 

[hyperionguy]

I recall seeing this theorized somewhere on the forum ... not sure where though.

You are correct. Other than people thinking it increased their filter quality by attaching to their return, it has only been theorized for backwash on this forum.

In theory it works. Practically, so far not so much. I hope to prove otherwise, which is why I hope y'all can help.

 

[duraleigh]

The purpose for backwashing into the pool is related to smaller Intex pools where a proper backwash has a significant impact on water levels as well as dilution of salt, Ph, TA, and borates.

1. A five minute backwash loses about 130 gallons (about 65 cents) with your pump, if that, and I doubt you backwash for five minutes, but maybe.

2. Your salt drops 3%.

3. Ph remains unchanged.

4. TA remains unchanged

5. borates drop 3%

I still don't understand.

 

[hyperionguy]

There are many reasons to backwash back into the pool.

Color me obtuse but I can't think of one.

Do you think you read about those bags on this forum?

I mentioned my reasons in the last paragraph.

The pool I grew up maintaining at my parents house, when I backwashed their DE filter it had an immaterial affect due to the large quantity of water in the pool. It's a different story all together.

Yes, I did read about those bags here... plus someone PM'ed me about it, but I won't expose them here.

 

[hyperionguy]

The purpose for backwashing into the pool is related to smaller Intex pools where a proper backwash has a significant impact on water levels as well as dilution of salt, Ph, TA, and borates.

1. A five minute backwash loses about 130 gallons (about 65 cents) with your pump, if that, and I doubt you backwash for five minutes, but maybe.

2. Your salt drops 3%.

3. Ph remains unchanged.

4. TA remains unchanged

5. borates drop 3%

I still don't understand.

It is somewhat about chemistry, but more about wrecking my yard with all of the discharge. Cost of water isn't much of an object.

 

[gtemkin]

Makes perfect sense to me. Trying to minimize water and chemistry usage, to only what's really necessary. Sounds like the same precepts of BBB that most of us practice.

I've done the same thing except I used a medium sized industrial cartridge filter which I found surplus. Worked fine. Idea is to backwash the gunk from the sand filter and then do a quick rinse of the cartridge - with a lot less water and chemistry wasted especially if your clearing a pool of a severe algae bloom and have to do multiple backwashes. It's really not at all difficult. As others have said, a bag just ain't up to the task.

 

[duraleigh]

If you are dedicated to saving the 3% (I think it's even less) of backwash, why not backwash into one or two 55 gallon plastic barrels?

Next, take that filter bag, turn it inside out and secure it on the end of a garden hose.

Then, stick the bagged end of the garden hose into the barrel and create a siphon that moves the backwash water through the hose and into your pool.

 

[gtemkin]

If you are dedicated to saving the 3% (I think it's even less) of backwash, why not backwash into one or two 55 gallon plastic barrels?

Next, take that filter bag, turn it inside out and secure it on the end of a garden hose.

Then, stick the bagged end of the garden hose into the barrel and create a siphon that moves the backwash water through the hose and into your pool.

Think that's a great idea. No real specialty equipment needed!