Backwashing according to pressure gauge or not?

[sparkwatercleaner]

I've checked the pipes, and these "unions" seem to be sealed with some sort of plumbing glue. Anyway, I'll try to open the filter when I have some time.

[sparkwatercleaner]

I've made the following test!


1- After having backwashed, saw the pressure gauge.
2- Stopped the pump and set the multiport valve to "closed".
3- Turned on the pump, rapidly saw the gauge, immediately turned off the pump.
4- Set the valve again to "filter".

What I got to know from this was that the maximum pressure my pump could do was 10 psi higher than the pressure at normal filtering, I simulated a completely clogged filter, with no water passing through it. So, in my case, if I wait till the pressure of the filter gets 10 psi higher than the normal filtering pressure , my pump will break down, as there would be no circulation. This means, again, in my case, that I've got to backwash when pressure gets 6 psi higher and no more.

Do you agree (and understand what I explained)???

[mr_clean]

How often do you need to backwash your filter?

[sparkwatercleaner]

How often do you need to backwash your filter?

I run my filter 5 hours a day during swimming season, which comes to be right now here where I live.
I backwash my filter once every 2/3 weeks.

[mr_clean]

what size sand filter do you have? It should tell you on the side of it.
what size pump do you have? it also will tell you.

[sparkwatercleaner]

What d'you mean by size?
It says:
Width D: 430
Height H: 875
Height M: 735
Height N: 655
(I think they are Millimeters)
Flow rate: 7 m3/h
Pool volume: 40.000 liters
Filter sand: 60 kg
Model: Astral - Millenium - 22407


The pump:
HP: 1/2
Flow rate: 7.8 m3/h
Model: Astral - Sena - 25462

[mr_clean]

what Brand? meaning who makes it? Hayward - Pentair?
take a look at this
Hayward filter here is this your filter?

or Pentair filterhere

[sparkwatercleaner]

Both the pump and the filter are AstralPool, a Spanish brand.

To see my filter, see this page, select "English" on the bar, select "swimming pools", select "filters", select "sand filters", select "Blow-moulded filters", select "MILLENIUM filter". Mine is the one on the first picture, second on the chart. There is a downloadable "manual" with technical information on its last page.

To see my filter, see the same page, select "pupms", "self-priming pumps", "plastic self-priming pumps" and then "SENA pump". Mine is the second on the list, the 1/2 hp pump.

Note: My filter's gauge has different colors indicating proper pressures. 0.8 bars is in the upper part of the green area of the gauge. But notice that my pump's technical info states that its pressure is 8 m.c.a. which is the same as 0.8 bars. 0.8 bars are 18 psi approximately. The green area goes from 10 psi to 20 psi. When running with a clean filter, the gauge reads 9 psi. I have to backwash approximately at 14 psi.

[sparkwatercleaner]

Anybody has an answer to my question, instead of making more questions?

[Larry]

I regulary clean my sand filter when the backpressure shown on the gauge is more or less 4 to just 5 psi higher than starting pressure, and all the equipment, togethter with the pool, is new. I've got to do this 'cause if not, the skimmer (just one, it is the only suction device which has its valve open) won't collect the debris because of low suction. Is this ok? Any problem if I do so?
I ask 'cause I've been told just to backwash when the pressure gets 8-10 psi higher.

I backwash my filter once every 2/3 weeks.

We recommend running the filter 6 - 10 hours per day in the summer (or two turnovers, whichever is greater). We also suggest backwashing sand filters every week or 10 days to keep the sand light and "mobile".

According to your specs, the 0.5 hp pump is providing the filter with a flow near its maximum limit so any accumulation of dirt in the filter will result in an immediate drop in backpressure through the filter. In our Mediterranean climate, I would recommend our customer with your setup to:
* run the pump for at least 9 hours a day in the summer
* backwash once a week

Frequent backwashing can be a waste of water and chemicals, but poor circulation is potentially worse. With a pump near the limit of a sand filter's capacity the most frequent problem we encounter is sand loss due to the speed of water flow during backwash. If the filter is losing sand, you should see some grains left behind in the sightglass after backwashing.

A quick inspection after about 6 months of regular use will confirm whether you have any sand loss or not. The Astral filter lid is very easy to remove using the two-handed key they supply with the filter. Sand loss is typically diagnosed by lower filter pressures as the water flow increases through the reduced sand bed.

I hope this answers your questions.

[sparkwatercleaner]

Thank you Larry.

To open the filter, I will need to unscrew the pipes attached to the multi port valve, but I have no experience in doing this, and the screws seem to be sealed with glue. What should I do?
Sand came out from the filter the first 4-6 times I backwashed, now sand isn't coming out when backwashing or is either a very small amount of it. I told the pool guy about it but he said it's normal... huh.
Starting pressure decreases slightly every time I backwash.
According to you, I should get a new and bigger filter? (I'm not willing to spend a lot of money...)
What confuses me is that pressure never rises the "green" part of the gauge, nor it did when I ran the pump with the multiport valve closed.
I run the filter 6 hours a day and it seems to do the job, thew pool just gets slightly cloudy when it is used by many people.

[Larry]

Sand came out from the filter the first 4-6 times I backwashed

This can be expected in a new filter, when we tend to overfill slightly and the new sand hasn't had time to settle yet.

Starting pressure decreases slightly every time I backwash.

Could indicate ongoing sand loss or calcification of the sand resulting in "channeling".

According to you, I should get a new and bigger filter?

You mention that the pressure stays in the green - you do not need to change the filter. The pump/ filter specs seem a little off but it sounds like your setup is OK.

What confuses me is that pressure never rises the "green" part of the gauge, nor it did when I ran the pump with the multiport valve closed.

If you want to make sure the pressure is rising, don't close the 6-way valve. Try closing the valve on the return line to see the increase in backpressure. Never close it all the way or you risk bursting the filter (it's only blow-moulded after all).

To open the filter you need to unscrew the collar holding the multiport valve onto the filter. If there is not enough play in the pipes you will have to remove the multiport valve to get to the sand, but it sounds like there are no threaded unions for easy opening. I would ask the people who put the pool in for guidance to remove the multiport valve.

[sparkwatercleaner]

My fears have come true! Sand is STILL coming out from the waste line when I backwash. I've just noticed it. It is almost a handful of sand. Also, the pressure gauge shows less starting backpressure than the last time I backwashed. These means just one thing: that the pump is oversized for the filter, right?
I'll contact my pool builder. The filter and pump are both under warranty, so I expect him to do something.

[Larry]

I would guess the filter is too small for the pump.

The other possibility is someone forgot to put the diffuser head on the center pipe (if your filter comes with one), or you could add a diffuser to see if it helps.

When the pump is too powerful, the pressure guage tends to be high initially; do you remember if the pressure guage was always in the yellow/ red in the beginning?

[sparkwatercleaner]

When the pump is too powerful, the pressure guage tends to be high initially; do you remember if the pressure guage was always in the yellow/ red in the beginning?

No. That is what confuses me!!! It was always pointing the beginning of the green part!!!