DE in sand filter

[larry2338]

We have a problem with fine red dust in the pool that our sand filter can't seem to handle. I'd prefer not to vacuum a couple of times a week if I don't have to. Just wanted to double check that it's OK to add a cup or two of DE through the skimmer bringing the filter pressure up 1 lb. Sort of hate to do that as my pressure consistently runs 26 lbs now. (Builder who was otherwise excellent would not think of installing anything less than a 2 hp pump on a 1 1/2" system.)
I'm not overly concerned since the max. operating pressure is 50 lbs on the 325lb Pentair. If I add the DE and brush the pool regularly, is there a good chance that this will solve the problem?

[waste]

larry;
a little DE in a sand filter can help get the smaller particles out of the water. (I think it was CarlD who posted a method of adding it to a sand filter- just search for his posts and you should find it) I'm not sure that DE can get it out, without chemical help. There are posts that give you more info, but you'll have to "search" for them, there's something about a trichlor puck, in the skimmer, that is supposed to help.

[duraleigh]

Hi, Larry,

Al (poconos) will be along soon...he's the one who, I think, initiated the DE idea.

That normal psi of 26 seems okay but somewhat on the higher end of average. I wonder if that big pump is forcing the water through your filter too fast? Might be causing some channeling or maybe just forcing the silt thru the laterals.

The DE is the easy fix. If that doesn't work, I'd take the top off my filter and see what it looks like in there. If you decide you're pushing the water too fast into your filter, you could restrict your suction lines at the ball valves and your pressure (and flow) will drop immediately. I know that may go against normal thinking but it actually hurts nothing and reduces your electric bill a little since the pump is constant speed. Again, the DE would solve it most easily.....just watch your pressure.

Dave S.

[Poconos]

Larry,
Well...I didn't initiate the DE idea, it was really brought up a real long time ago but I've been mentioning it for a while. 26 PSI does sound high and that agrees with the 2HP pump scenario etc. What would be interesting to know is the blocked pressure the pump is capable of. If you know this then you can get an idea of how close to the max pump pressure you are operating. Do you still have good flow from the returns? Raising 1 PSI won't hurt anything. As for the trichlor puck in the skimmer....don't see how that would do anything constructive except add CYA and chlorine. Me thinks that your idea of adding DE and brushing regularly will indeed solve the problem. Dave's idea about filter channeling is valid. Also his comment about cutting flow is valid but I really don't know if I'd do it by restrictions via the suction or pressure side. Never thought about it. Turns out on a centrifugal pump a totally blocked flow is minimum motor current because no work is being done moving water. If anyone doubts this throw a clamp-on ammeter on a motor line and try it. Looking back in my records, 17 May 2001, at 15 PSI got 7.51 amp, flow blocked at 26 PSI was 6.4 amp. (240V motor on a 1 HP Hayward superpump.) I know...I'm a sick puppy for keeping records of this stuff. I need another Scotch.
Goodnight.
Al

[larry2338]

Thanks for the replies. The flow from the returns is excellent. 16x32 IG vinyl SWG with 4 return outlets. I think the high pressure is simply the pump being oversize by a factor of at least 2x. I've wondered about channeling in the filter but doubt that I'll check that this year. I'm going to add DE and see how it works. Thanks again.

[Poconos]

In case you didn't see it in other posts when you add the DE do it slowly, maybe 1/2 or 1 cup at a time and give it 20 minutes or so for the pressure to stabilize. Seems to take some time. Once you're calibrated you can chuck in the right amount at once after backwashing.
Al

[waste]

Larry,
Well...I didn't initiate the DE idea, it was really brought up a real long time ago but I've been mentioning it for a while. 26 PSI does sound high and that agrees with the 2HP pump scenario etc. What would be interesting to know is the blocked pressure the pump is capable of. If you know this then you can get an idea of how close to the max pump pressure you are operating. Do you still have good flow from the returns? Raising 1 PSI won't hurt anything. As for the trichlor puck in the skimmer....don't see how that would do anything constructive except add CYA and chlorine. Me thinks that your idea of adding DE and brushing regularly will indeed solve the problem. Dave's idea about filter channeling is valid. Also his comment about cutting flow is valid but I really don't know if I'd do it by restrictions via the suction or pressure side. Never thought about it. Turns out on a centrifugal pump a totally blocked flow is minimum motor current because no work is being done moving water. If anyone doubts this throw a clamp-on ammeter on a motor line and try it. Looking back in my records, 17 May 2001, at 15 PSI got 7.51 amp, flow blocked at 26 PSI was 6.4 amp. (240V motor on a 1 HP Hayward superpump.) I know...I'm a sick puppy for keeping records of this stuff. I need another Scotch.
Goodnight.
Al

Al, Dave, Larry,
To clarify, I thought the 'rust' colored particles were iron, therefore the trichlor puck suggestion, used with a 'metal out' product. If the filter IS channeling, either the pump is too much, or the sand is impacted and needs to be replaced. If the filter is below pool level, there is an increase in pressure.
After a little thought, it occurs to me that the number of returns may be too small for the amount of suction. (1 or 2 skimmers and a main drain would be too much for 2 or 3 returns - the pressure would be in the area that Larry describes)