How long do you spend doing it ?

[Spainboy]

Hi guys , thanks to those who steered this newbee in the right direction a while back .
So , SWG and pH doser installed and working as expected , here in a sunny northern Spain .
I run the SWG at 50% , no need to add any muratic acid in the first 2 months since pool re-build , and it is peak summer weather right now .
The pH doser has maintained a rock steady level at all times .
Not even had to add any more salt yet .

What is problem then ?...... I hear you ask !
I have just replaced the ancient Hayward pump that ( when in use ) had been likened to the noise of the space shuttle during take-off .
The new Hayward 1HP Max Flo XL variable speed , which came with all the usual manufactures claims of saving electricity due to the permanent magnet motor .. blah , blah ,blah !
I liked the idea to run it 24/7 ( as Hayward promote ) so I could generate salt/ chlorine during the night , as ( apparently ) this is the best time to do so .

I have set the pump at 1200rpm for 20 hours , and 2400rpm for 4 hours . surely enough for 48m3 pool ?
The bit I did not consider is - the pressure on the 600mm sand filter would drop to just above zero when at 1200rpm - this lead me to think ......would the filter be functioning correctly ?
Surely its water passing through sand - just slowly - but for an extended period - therefore enough .
Doing some research on this site ( and elsewhere ) I am now more confused than ever .

There is no cost benefit of night-time electricity , and most here do the 8 hours at motor full speed method .
Spain can be slow to pick up on new ideas , and most pool owners here are rich and get the pool guy to do it all so have no clue .
Sadly I do not have this financial benefit , so need to ask for help . Cheers . Spainboy .

 

[mknauss]

Your low speed is fine for filtering. Actually better. Up to you if you want to run 24 hours per day. Not necessary but fine if you want to. Just be sure you run the pump and SWCG long enough to generate the chlorine you need each day.

 

[Spainboy]

Hi mknauss ! knew you would have a steer for me .

On the low speed actually filtering better......... then maybe I go even lower ? ? ( 600rmp is the programmable minimum ) .

Also don't know if the 35g/hour SWG will have a minimum flow rate to function .

 

[mknauss]

The SWCG will control how low of rpm you can go. Also at what rpm does the flow rate still skim the pool surface.

To test. Start at 1000 rpm. Does the SWCG work? If not, go up 100 rpm. Do that until the SWCG will work. Then add 100 rpm and that will be your minimum rpm to run the pump to generate chlorine.

With my VS pump, once I get to about 1500 rpm, the flow switch will not stay closed. At 1200 rpm, the flow does not skim my pool. Yours will vary as you have a different pump.

 

[Spainboy]

Update - I experimented as suggested with RPM's to produce chlorine .
Although the chlorinator was producing at 1000rpm ( and even lower ) - below 1100 the usual bubbles of gas were starting to form into a void in the top of the chlorinator . I quickly boosted the pump to " wash through " any buildup . So 1100rpm is my practicable minimum whilst producing chlorine .
The question is now ........ if I am to run less than 24 hours a day ........... With 4 hours a day total at 2400rpm to skim the top ....
how do I calculate the amount of hours to add at 1100rpm to get the equivalent of the benchmark 8 hours a day filtration ?
Is it just 4 x 2400 = 9600 divided by 1100 = 8.73 hours , or is that a too simplistic ( therefore inaccurate ) formula ?
Any better way to calculate - please advise !

Your thoughts are appreciated .

 

[mknauss]

There is no 'benchmark' hours of filtration. It is what your pool needs to create the chlorine, skim the surface to your satisfaction, and filter the water to your satisfaction. Start with how long you need to run the SWCG to create the chlorine. If that is not long enough, then reduce the generation level and add a couple hours run time.

 

[Spainboy]

Hmmm....... Interesting .
When choosing the correct propeller to put on your speedboat for optimum performance ( i.e. no. of blades , pitch etc ) it is always difficult to get it right first time .
As someone once put it to me " its part science , part voodoo magic " - it appears getting pool filtration perfectly set up has the same methodology .

I understand that filtering for longer than the minimum necessary can never be a bad thing , but excuse me if this is a silly question ,
...... how do I know if the water is correctly filtered ........ is it just clarity to the eye , or is there a particular scientific test to indicate ?
and , if so , what levels should I be looking for ?

 

[mknauss]

how do I know if the water is correctly filtered

Clarity. That is really the only factor from a filtering standpoint.

 

[Spainboy]

Thank you once more mk . I have a waterking cyclonic pre filter which is brilliant at removing wind blown dust , seagull poo etc -
thus preventing it getting into the filter sand . There is no leaf / grass debris .
The pressure on the filter has barely raised in the 8 weeks I have been going since first fill .
I decided to backwash anyway today as it has been such a long time . The multiport glass cleared in less than 2 minutes , so I then did a 1 minute rinse .... done .

The question is ...... how log do I leave it till next time ( assuming there is little rise in filter pressure ) ?
Some blogs say backwash every week , but I know of no-one that does this as it is overkill .

 

[CrystalRiver]

Wait until the pressure rises 25%. Anything more often is wasting water and chemicals. So is a one minute rinse - 15-30 seconds is plenty.