pressure problems with new de filter

[coryinsocal]

From what you describe I assume you have an in-ground pool with the filter and pump above the pool waterline. If this is the case then nothing will prevent water from flowing back to the pool through the skimmer and return lines when you open the system to air. There is not normally a check valve in the skimmer line. Some situations...maybe. I don't have a DE filter so I ask, why do you want to drain the filter? If it's to work on it then I don't know how to prevent DE from backing through the skimmer. Hopefully someone with experience with DE filters will kick in. Not much help here.
Al

yup, IG, and the only reason to drain was to inspect the grids or clean the filter. not really concerned with it going back through the return (there should be de on that side). i guess i could add in a ball between the pump and filter, but this is another, more solvable issue. mostly i'm concerned with the pressure/de problem.

[Tomcat]

When I backwash and add new DE, I hardly get a pressure rise as well (maybe 1 or 2 psi).

[coryinsocal]

hmmm, so before the de there's no pressure on the gage? problem i've got now, is there was no pressure even after 8 of the 12 oz coffee cans of de (i know these are only 3/4 lb, but i figure that should have at least gotten me some pressure.)

[Tomcat]

Oh..........zero pressure. Bad gauge? If the pump is working, you've got to have some pressure.

[coryinsocal]

that's why i was thinking maybe valve, if the water had 2 pathways, maybe it wouldn't build pressure...

[Poconos]

Tomcat is right. The pressure gauge is located on the pump output port, or the filter inlet...same point. You should be seeing some pressure under any condition.
Al

[coryinsocal]

ok, so i realize i'm getting carried away with the stream of thought, so i'll simplify this post.

-valve works now
-gage works now

i think i need to re-ask the pressure question and i'm pretty sure that'll tell me where the issue is...

how much is the normal increase in pressure over brand new, no de on grids and grids with the recommended amount?

if it's significant, i'm realizing that my plumbing is kinda hacked and i have significantly more return than suction. my pool is about 50 years old, has a vintage 3/4 horse pump, and originally had a 1.25" suction and a 1" return. sometime, someone scabbed on an extra 1" return that just dumps over the coping.

so i filled up again, and had my wife watch the gage on the filter while i put my hand over one of the jets, it read about 2-3psi. at this time i figure there was less than half(maybe less than 1/4) of the needed de. when i let go, it goes to zero.

i'm wondering, with this small of an inlet, and minimal line backpressure, would a 36 sq ft even see much pressure until the thing had the full amount of de? i realized that i never maxed it out. i probably got to about 75%.