No drain water exchange help

[catsncoffee]

I'm currently in the middle of a no drain water exchange, but my subpump is pushing out water a lot faster than my hose is filling. Subpump rate is 20 gal a minute fill rate with my hose is only 6gal minute. I don't want my water level to get too low because it's going to be nearly 100 degrees tomorrow in AZ and I'm concerned about the plaster. Should i let it drain down a few inches then turn it off until the hose can catch up? How do i figure out how long i need to run this to exchange enough water to lower my CH?

 

[mknauss]

Did you measure your fill rate with a 5 gallon bucket before starting?

If you need to turn off he sump pump for a few hours to let the hose catch up, no issue.

 

[catsncoffee]

Yes did the 5gal bucket fill with the hose and with the water coming out the pool via the sub pump. Hose fill is pretty slow. Ok thanks i will just shut it off when it gets too low and let the hose catch up. How do i calculate how long i need to run this water exchange for?

 

[mknauss]

How many gallons do you want to exchange? Use the bucket rate and determine how long to run the pump to remove the amount of water you need to .

 

[catsncoffee]

CH is over 1000 so just trying to drop that as much as I can. Fill water is hard about 400.

 

[mknauss]

In Phoenix your fill water should be around 250 ppm. If your current pool CH is 1000 ppm, you need a full drain. Doing the exchange, it is not as efficient as a drain. So you will need to go to 16000 gallons or so.

 

[crusemm]

If you were using water with 0 ppm CH, to dilute from 1,000 ppm to 650 ppm (the maximum acceptable) You would have to drain 4,900 gallons and refill with fresh water. With a refill of 400 ppm CH, you have to replace 9,000 gallons of your current pool water. this will achieve a CH of 615 ppm.
M1V1+M2V2=M3V3 Solve for M3
(1000 ppm)(5000 gal) + (400 ppm)(9,000 gal) = M3(14,000 gal)
(5,000,000 ppm-gal + 3,600,000 ppm-gal)/14,000 gal = M3
8,600,000 ppm-gal / 14,000 gal = M3 = 613.3 ppm

After Marty's comment, if your CH is 250, that changes the math. I come up with a final CH of 518 ppm for the same volume exchange, if you want a lower CH you have to change out more water.
Also doing a no drain water exchange your change in concentration won't be that precise due to mixing

 

[catsncoffee]

Thanks! I'm in the Phoenix area but under a different water company that most of metro phoenix, so i dont know, my fill water seems higher. My PPM meter is reading 400 and the last time i drained and refilled it was at 400 when i tested CH after the fill. 615 will get us by. I am looking for a company to come do an RO exchange but having a hard time locating one that isn't charging over 1k.

 

[crusemm]

What's the cost of your water? That 615 ppm calculation is a drain/refill. If your water cost for approximately 10,000 plus gallons of water is lower than 1K, an RO changeout might be cheaper. Or look into buying an RO setup and DIY?

 

[crusemm]

Looking at this Old Thread and specifically this quote from Joyful Noise in Tucson pretty much sums it up: Drain, refill, top off with water from a softener.

The cheapest way to deal with the buildup of chemicals in water in most areas is to simply drain and refill. I know no one likes to see thousands of gallons of water go down the drain, and it can be inconvenient if you are on a well, but it is almost always cheaper to drain and refill.

Draining and refilling my 16k gallon pool would cost somewhere in the neighborhood of $250-$300 (using municipal water and having to pay for the sewerage fee even though I would drain it out onto my property). RO in my area costs at least $300 to perform and will still require me to supply both the electrical energy to run the pumps and additional make-up water to replace the waste fraction that RO generates. That would cost me at least another $100 dollars in water. Even with all that, the RO process would only get me to about 250ppm CH and it would take 3 to 4 days for the RO process to be completed. I can drain and refill my pool in about 2 days.

Unfortunately, there really is not any small scale filtration technique that will work for residential pools. Once a pool is refilled with fresh water that's low in CH and CYA, then the best approach is one of prevention - don't use stabilized chlorine products and, if possible, use only water from a softener to refill a pool.

 

[catsncoffee]

It adds about an extra $90 to our water bill when we do a full drain and refill.

 

[mknauss]

My PPM meter is reading 400

You need to use a Taylor test kit.

 

[crusemm]

It adds about an extra $90 to our water bill when we do a full drain and refill.

So that looks like a no brainer to me, Drain, refill adjust chemicals. Also as Marty says, use the Taylor kit. Way better (also read the test right, learn from my mistake)

 

[catsncoffee]

Good point i'll do a test on the fill water with my kit. Thanks for the help!