Backwash question.

rsharp

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Jun 12, 2010
129
im in the process of turning my swamp into an oasis lol! im at the point now where my water is a bright cloudy blue. at first i was having to backwash every two hours. now nothing is left but the tiny clear particles clouding up my water. the past couple days my pressure has been rising very very slowly. like 2 psi a day. i decided to backwash anyways and the water was still disgusting. my question is are these particles slipping through the sand filter? (thats why the psi isnt rising) and should i still be waiting for my psi to rise 10 before i backwash even though the water is nasty after a 2 psi change? Also im gonna buy some DE (pool grade) tomorrow and add a little to the sand filter. maybe that will clear up my problem!!
 

jblizzle

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May 19, 2010
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What is your "clean" pressure reading? There is a new(er) recommendation of backwashing when the pressure goes up by 25% maximum of the normal pressure instead of the +10psi rule. This keeps your filter doing its job a little better as having a 10psi increase could significantly cut your flow. You can always backwash more often if you wish.

I would say though that since the pressure is rising, you are certainly catching something in the sand. Does any of this settle on the bottom that you could vacuum to waste?
 

duraleigh

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What you are experiencing is normal and correct. The filter is still catching debris.....that's why your backwash water is dirty.

We are changing the suggested backwash procedure to 20-25% of clean psi rather than 10 psi.

If your clean psi is 10, then you should back wash somewhere around 13. If it's 20 psi clean, then backwash around 24. etc.

Waiting until you get a 10psi increase reduces your flow (and efficiency) way too much.

It will eventually clear on it's own but the DE may make it go faster.

Oops, jb beat me to it so I'll just post to reaffirm.
 

mynewpool

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Mar 17, 2010
1,082
Spring, TX
duraleigh said:
What you are experiencing is normal and correct. The filter is still catching debris.....that's why your backwash water is dirty.

We are changing the suggested backwash procedure to 20-25% of clean psi rather than 10 psi.

If your clean psi is 10, then you should back wash somewhere around 13. If it's 20 psi clean, then backwash around 24. etc.

Waiting until you get a 10psi increase reduces your flow (and efficiency) way too much.

It will eventually clear on it's own but the DE may make it go faster.

Oops, jb beat me to it so I'll just post to reaffirm.
Not to intrude, but why have yall decided 20-25% is better than the 10 PSI increase?
 

rsharp

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Jun 12, 2010
129
a "normal" reading on my guage is 50. (gauge max is 60) i would usually wait for it to get almost to 60. at that point the water pressure coming from the return was cut in half!! it would also take over 2 minutes back washing for the water to get clear. thanks for all your all's help!!!
 

jblizzle

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mynewpool said:
Not to intrude, but why have yall decided 20-25% is better than the 10 PSI increase?
Well the OP is a perfect example:

Going from a normal pressure of 10psi to 20psi is a 100% in pressure and large reduction in flow. Going from 50psi to 60psi is only a 20% increase in pressure so the flow reduction will be less. Therefore, a % recommendation is more universal and keeps the filter working pretty efficiently.
 

jblizzle

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rsharp said:
a "normal" reading on my guage is 50. (gauge max is 60) i would usually wait for it to get almost to 60. at that point the water pressure coming from the return was cut in half!! it would also take over 2 minutes back washing for the water to get clear. thanks for all your all's help!!!
:shock: And I though 30psi was high. Have you always had such high pressure as that does not seem normal ... either the pump is WAY oversized, there is some type of restriction, or your gauge is bad.

Does the gauge return to zero when the pump is off? They are pretty cheap to replace and verify, but if the pressure is really that high, I would think something should be "fixed"
 

rsharp

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Jun 12, 2010
129
when the pump is off the psi reading is like 45. i guess that would indicate the gauge may be bad? the gauge is roughly 9 yrs old. when we bought our pool we were sold products that were to big for our pool.(WATSONS) im guessing so they can maximize they're profits!! my sizes are listed in my signature.
 

Bama Rambler

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We've also found out that on a lot of systems the flow out of the return(s) is/are greatly diminished well before they see a 10 psi rise. Since my normal pressure is 11 psi, the flow gets to be almost non-existent by the time I see a 10 psi pressure rise. However, at a 25% (~3psi) rise, the flow is tapering off and I know it's time to backwash.
 

jblizzle

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You equipment does not seem too big to me (at lease compared to others I have seen).

I would suggest you replace your gauge so you have a better feel of when you should be backwashing. Should be available at HD/Lowes/pool store. Probably could get away with a 0-30 gauge ... but 0-60 is another option.
 

duraleigh

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Any pool gauge should read zero when the pump is off. FWIW, about the max pressure a pool pump can produce is 35-40psi, even if it is fully blocked on the pressure side.
 

rsharp

Well-known member
Jun 12, 2010
129
u guys are good! i love it! thanks for the help you guys. i will be sure to replace my gauge!!