We purchased our home in New Jersey last september with an in-ground 28,000 gallon pool serviced by a Pentax DE 60 sq feet filter. When we closed the pool, we took the DE apart and cleaned everything out and further put it back together when we opened up last week. When I started things up I added about 9 scoops of DE over 2 days(as recommended by pool opener). The pool was initially cloudy but then I ran the pump for about 2 days and it cleared out very nicely.
The pool looks great and the water is clean, yesterday on the recommendation of some friends I took a sample of the water to the local pool store and the pool dude sold me some of this phos free stuff which he told me to dump 1.5 liters of it into my skimmer and let the pump run for 24 hours and then add another 1.5 liters and run for another 24 hours. I dumped the first 1.5 liter and started the pump and I noticed that the DE pressure spiked up within about an hour to the 30 psi level. I did the backwash/rinse cycle and further refilled just 1 scoop of DE and let it run over night. Earlier this morning I saw that pressure was back up to 30 psi.
Late last night I was reading up on the pool chemistry stuff and I read a lot of comments about the pool store chemistry being a bit dodgy and the phosphorous stuff is not that important, but it is more important to get a handle on the overall water chemistry as outlined in the tutorials here. I have now ordered my pool testing kit(Taylor Instruments). Here are my questions.
1. Even before I added this phosphorous reducing agent, I felt that the DE pressure was spiking up quite a bit quite quickly, do I have to do a full clean up of the DE and start afresh?
2. After I backwashed I know I added too little DE, would that cause the issue of the DE pressure spiking high? When I get home later this evening do I just add the recommended 4-5 scoops of DE and start the pump on again?
3. How long should I run the pump everyday? 5 hours?
4. Did this Phosphorous reducing agent cause my filter to start working harder & hence the higher pressure?