Backwashing question

amin36 said:

1-what if the owner of the pool did not read the initial pressure gauge (clean filter pressure)?

Click to expand...

Clean the filter and read the clean pressure.

As a service person, you should have a general idea about what pressures are normal for different pump and filter configurations.

amin36 said:

2-Does changing the amount of water coming from main drain or skimmer by manually changing the valves change the pressure of the sand filter?

Click to expand...

It can in some cases and in other cases it makes very little difference.

You can try it to see what happens.

amin36 said:

1-what if the owner of the pool did not read the initial pressure gauge (clean filter pressure)?how should he or she estimate pressure rise in the case he doesn't know clean filter pressure ?

Click to expand...

Pentair filters have a dial on the outside of the gauge that you can rotate to set at the START filter pressure. If this is applicable, show this to your client. Once you backwash or clean the filter then you can set it to the new START pressure.
Also, remember to check the pressure at the same pump RPM - if you have a VS pump, the pressure will change with pump speed so note that as well with the client.

Those dials indicate a 10 PSI or 23' of head increase before cleaning which is very extreme and can lead to signification flow rate reduction. This is why we generally recommend the 25% rule instead.

It depends on the size of the filter and how much debris falls into the pool. I never reach 25% increase because I have a very large filter and clean it at least once per year.

More than likely if you are cleaning more than once per month your filter is too small. Ideally, it should be once per season but only cartridges really allow for that.

amin36 said:

Thanks guys for your answers.

One thing i have in my mind:

How often does it approximately take for an ordinary pool filter to get backwashed cosidering the 25% rule ?

I know the situation for each pool is different but as a general thing how long does it take?

Thanks

@mas985 @HermanTX @JamesW

Click to expand...

I have a DE filter and have several trees nearby so this time of year, I backwash monthly regardless. In summer I can go several months but I rarely hit the 25% guideline in summer. Fall and early spring are my 2 times that I need to backwash monthly.

Once maybe twice a year in my area and using skimmer basket nets.
We did have a couple summers with massive wild fires in the mountains resulting in ash accumulations on the pool surface. This required more frequent filter cleaning.

amin36 said:

Thanks guys for your answers.

One thing i have in my mind:

How often does it approximately take for an ordinary pool filter to get backwashed cosidering the 25% rule ?

I know the situation for each pool is different but as a general thing how long does it take?

Thanks

@mas985 @HermanTX @JamesW

Click to expand...

Agree with all advice given.

Also, your "clean" filter pressure needs to be physically recorded ASAP and archived for this client because this will slowly increase over time. Each time you clean or backwash a system, your system pressure may increase by a marginal or measurable amount. This will vary and is dependent on filter type and the debris it's accumulating.

You ideally would have a baseline at the filter/filter-medium's infancy; lacking this, you need a "clean" baseline as soon as possible to that date. As an aside, this advice applies to cartridge filters especially. (D.E. is a a little different animal because the baseline may vary each recharge.)

As far as how often to backwash, my team is taught it can't be done too often with a sand filter. We have very fine red sand in our area and it kills our flow within a week. You'll also find a short backwash done more often, is less disruptive than a long one done infrequently. I.E. less water down the road/in the yard, less water loss in the pool (don't have to close the skimmer if the pool is small and drains fast etc). This is likely overkill for most, but for our pools, yields the best result for a clean and happy system.

My only advice/warning if you do backwash often, is to make sure you get that lever on the multiport all the way down and don't twist/grind the plate against the spider gasket when you rotate. The dome top are easy to service but the flat tops are essentially impossible to do a gasket replacement on (they're glued in place with herculean cement).

amin36 said:

Thanks

Why do you backwash each week?is that because of that red sand in your area?do you reach the 25 % pressure rise each week?

Click to expand...

10psi increase and 25% increase are all informed suggestions for good reasons. You could argue which is better or correct. My opinion is it's unwise to be too rigid on one specific indicator when deciding what do and when; i.e. the pressure simply indicates pressure. I would never let a pool go 10psi above a prior-observed pressure read, but I would clean or backwash one early in a heartbeat if I was concerned about its status or what it was just tasked with cleaning up.

Being a service provider means you will need to learn the personality of several pools. You'll notice certain systems are much more forgiving than others in its relationship between flow and pressure, and will have different burdens from debris and bathers. You'll need to adapt your thresholds to each pool.

To answer your question, no, we don't necessarily do it each week. This was a general reference. We do it when we feel we've lost optimium flow or clarity anytime prior to a 10psi rise. We've backwashed 3 days apart many times.

Yes, our stubbornly fine red sandstone desertscape is a big reason. We also have commercial Vacation Rental homes and have people beating the pools to death each week. On these accounts, we have an entirely different support burden than we do for our residential. We have identical pools next door to each other that require a measurably different service on the same days because of their usage.

Takeaway: do it more often until you're comfortable doing it less. Learn the pools temperament and it'll save you a lot of trouble down the road.

bradgray said:

Takeaway: do it more often until you're comfortable doing it less. Learn the pools temperament and it'll save you a lot of trouble down the road.

Click to expand...

This statement is applicable to ALL pool owners. Thanks.

HermanTX said:

This statement is applicable to ALL pool owners. Thanks.

Click to expand...

Unequivocally.

The prior distinction was simply to illuminate to OP that pool maintenance is nuanced, and this is a lesson best learned early if one is being paid and entrusted with said maintenance across multiple pools.

The temptation for service teams can be to do at one account what you do at another, simply out of rote. And that's an invitation for headache and even potential heartache.

Something we learned the hard way at the beginning.