Pool Pump Speed & backwashing + fine dust

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H

Hawknz

0
Nov 30, 2015
44
Mardella, Western Australia
Hi All,

I've recently had to change the method of waste water disposal when backwashing and am wondering if it is necessary to run my variable speed pump at full power when backwashing? or will a low speed achieve the same result, even if run for longer?. At full power the volume of water coming out is huge and at a very high speed which with my new way I have to get rid of the water puts a lot of pressure on the pipe work away from the pool.

Secondly I have been away for 2 weeks and when I came home I'm not sure what the people who were looking after my pool did but I returned to a cloudy 'milky' looking pool. I live in a semi-rural area with trees all around my property so keeping the pool clean is always a challenge and recovering from green pool's has been something I've got very familiar with but on this occasion the pool was in a state I had not seen before, the water was a 'milky' white color and i could not see the bottom.
So I thought I would SLAM it and see if that helped, it has taken 6 days and 50 litres of liquid chlorine (unusually longer than normal) to get the pool back to a semi-clear state. However now what I am left with is this very fine dust coating the bottom of the pool, it is not grainy and when I try to pinch it it seemingly dissipates so I cant get a good look at what it is.
My robotic vaccuum is having trouble collecting it and strangely when I try to manually vacuum the pool it appears its going right through the filter and back into the pool again. I last back washed the filter yesterday, is it possible the filter is full again? I'm not sure how to get rid of this fine dust like stuff, would the glass media collect even this?

Any help appreciated,

Thanks
 
Hello Hawk! :wave: I doubt the glass media plays much a part in the dust appreance, althogh overall we tend to like sand media better here. Just an old "tried & true" method we know works. But that's another issue. It does sound as though the white "dust" product you are seeing that is difficult to vacuum and shoots right back out might indeed be algae - or dead algae. If the pool was neglected at all while you were gone, it won't take long during your summer over there for algae to ramp-up. It might help us if you posted your latest test results. Also let us know what, if anything, may have been added to the water since all of this happened. Are you actively performing a TFP "SLAM"?

As for the backwash rpms, I don't have one, so another member like @Jimrahbe will confirm for us. Keep us posted and we'll see what we can do to help.
 
Look on your filter and see if it has a recommended backwash flow on the label.
Having said that, I don't know that you need to run the pump on the highest setting, but I would run it at a medium high speed. Sand filters need a certain flow rate through the sand in order to flush the debris from it, so running the pump at too low a speed could leave debris embedded in the sand.
 
Texas Splash said:
Hello Hawk! :wave: I doubt the glass media plays much a part in the dust appreance, althogh overall we tend to like sand media better here. Just an old "tried & true" method we know works. But that's another issue. It does sound as though the white "dust" product you are seeing that is difficult to vacuum and shoots right back out might indeed be algae - or dead algae. If the pool was neglected at all while you were gone, it won't take long during your summer over there for algae to ramp-up. It might help us if you posted your latest test results. Also let us know what, if anything, may have been added to the water since all of this happened. Are you actively performing a TFP "SLAM"?

As for the backwash rpms, I don't have one, so another member like @Jimrahbe will confirm for us. Keep us posted and we'll see what we can do to help.
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Cheers for the reply,

Done the SLAM process and it passed the OCLT last night

FC: 10
CC: 0
PH: 7.8
TA: 100
CH: 375
CYA: 40
 
Thats the issue, the water is very clear until I go and sweep the pool, which I have just done now and all the dust or whatever it is on the bottom has been stirred up now and the pool goes back to being cloudy again. I've just put the robo in the pool but I am not anticipating the filter is fine enough to collect that dust stuff.. so fustrating
 
This can be one of those tricky situations. You've done a SLAM, albeit it went quickly, but you did pass the OCLT. While we realize clear water is one of the 3 SLAM criteria, we have to be critical and ask ourselves some questions:
1 - Is there any chance the dusty residue is remnants of algae still begin killed somewhere? Passing the OCLT you would think no, but on rare occasions algae may be persistent in an area which is why we have 3 criteria - just in case.
2 - What you see may simply be 100% dead algae still trying to get filtered. In that case a filtration issue is possible. Given the fact you have glass media, it makes me wonder. If it were sand, we'd explore options like a sand filter deep clean or adding some DE to the sand, but in your case I'm not so sure that will help with the glass.

Honestly, this is one of those areas you'll have to watch and evaluate for yourself. If your chlorine remains consistent throughout the day without major drops, and you see no evidence of algae after the SLAM with crystal clear water, you may have to open that filter at some point and inspect. You might also consider how reliable the glass media is in obtaining the filtration you desire. While brushing stirs-up that stuff, keeping it moving is an essential part of the cleaning process to get it to the filter. However if it's slipping through the filter, it can be frustrating.
 
bgpbucko said:
This dust at the bottom of the pool - can you just vacuum it to waste?
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Absolutely! Do the best you can without stirring it all up. Once you get the majority of it up, then you can see if more is generated. That would be a good indicator of something that is continually happening.
 
i'm now quite convinced this very fine particles are returning into the pool again after being through the filter. I have just vacuumed the pool and was watching the return jets and its quite obvious something is returning back in the pool again.
I've never tried vaccuum to waste before, i'm guessing having it goto waste will use a lot of water with the pump running very quickly, i'm guessing you have to be very quick or turn the pump speed down?? my waterline would be below the skimmers within a couple of minutes if i did it at the rate I backwash?.
 

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Hawknz said:
i'm guessing having it goto waste will use a lot of water with the pump running very quickly, i'm guessing you have to be very quick
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Yes, and if you don't have a drain and only skimmer, time is of the essence. But at some point you'll need to find out why the "dust" is slipping through the media. Either the media is overloaded (happened to me years ago with algae before TFP) or that glass simply isn't cuttin' the mustard.
 
Hawknz said:
but it seems since that sand is still a favourite on TFP?
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Some things are simply tried & true. Sand never goes bad unless someone "makes" it go back by adding pool store junk, so it's very reliable. For your SWG, it may be time to check the plates for scale build-up (if any). If they're ~ 5 years old, it may be their time. Even if so, you can chlorinate manually with regular bleach. Hang in there! The season is almost upon us. :swim:
 
Glass media is now more common in Aussie than sand, most suppliers don’t stock pool sand anymore. A mate of mine has a generic brand and thinks its the ducks guts. I have the poolrite brand and wish I hadn’t. I have had a very fine dust like powder go strait through before. It really helps if you add some DE but DE can be a little hard to find. The DE makes the filter artificially dirty - a dirty filter filters better than a clean filter. You need to keep an eye on your pressure though. The only other option is vacuuming to waste.
 
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