DE filter backwash (newbie)

Hi,

I just bought a home that has an in-ground pool with a Hayward DE filter (60 sq ft filter surface). 2hp Hayward single-speed pump. By my yardstick measurements, pool volume is approx 25,000 gallons. The home is seven years old, and I believe the pool equipment is roughly the same age.

I backwashed for the first time today. Pressure reading prior to backwash was 22 psi. I backwashed for about 2.5 minutes (until it looked like the water was relatively clear). The filter calls for 7.5 lbs of DE. The home's previous owner told me he usually added 5 lbs of DE after a backwash, so that's what I did this time. Pressure reading after backwash is 18 psi.

Am I in the ballpark here? I was expecting a bigger drop in pressure after the backwash, but I have no prior experience as a pool owner.

Thanks,

hikernut

If the pool has been clean and clear, it takes a very long time to build up "back-washable" gunk in the filter--I usually only backwash my pool 3-4 times a year, unless I have an algae bloom or something, so that pressure of 18 psi may very well be a good "clean" pressure.

When you turn the pump off, does the gauge go to zero? And then does it consistently come back up to the same number when you turn the pump on? If so, then the gauge would appear to work and I would think your pressure reading is fine. I'm sure some of the other DE filter folks will chime in with opinions (I have a sand filter) but I think it's okay.

My post backwash pressure is 12psi. I backwash when it climbs to 20psi.

Given the fact your post backwash pressure is 18psi, you may want to consider opening it up and cleaning the grids. You really have no way of knowing the last time that was done so might as well start from scratch.

Thanks for the feedback... really appreciate it.

Yes, the pressure gauge reads zero when off, and goes to same value each time it's turned on, so it seems the gauge is okay.

I did a bit of brushing the two days before backwashing, which was some combination of sand and/or algae, and I definitely saw that coming out of the backwash hose.

I'll take the filter apart and take a look in the near future...

hikernut

My brand new filter the 3620 started at 18 when i turned it on (pool was green at the time)..it always returns to that level..i backwash at 28-30.
i thought it should be the starting pressure should be from 8 to 10 ..but i guess not
I've had to back wash every 2 hours except for sleep time since and the pool is almost ready now.

I am not familiar with what normal pressure should be on a DE filter since I use a sand filter on my pool, but I can tell you that algae clogs a DE filter fast. Hopefully someone else will chime in who can tell you more about what normal pressure should be.

Couldn't clog a brand new filter within a minute..but it seems to be working fine anyway

I open mine up and clean grids after every 2 backwash and recharge cycles . not that hard . see what pressure reading you get on rinse cycle . you could have backpressure by a blockage or partially closed valve

ok thanks..i have another question..
when do i open the valve on the top to let air out? (other than opening it up to clean it)

After a backwash I let the pump run long enough to get a good circulation going and then I open it to bleed to air pressure off.