If I looked at the sand in the filter, what should I see?

[aquarium]

Bought the house w/pool April this year and have slowly been rebuilding things to make them work better. It's an IG 15,000 gallon plaster with a sand filter, probably at least 10 years old.

Not knowing how the pool has been managed in the past, I'm curious what I would find if I opened the top of the sand filter and looked in. It -seems- to be working okay, but I never see anything in the backflush glass thingy. If I opened the top and looked at the sand, what am I looking for, good or bad?

Thanks,

TW

[waste]

TW, good would be clean fluffy sand. Bad would be black - grey - green film on the top, or visible channels in the sand. However worst would be ... no sand! If you decide to pop it open, stick a finger in there and see if it resists some gentle pressure, you can't always tell by sight how the sand is holding up. Should you open it, let us know what you find.

[tenax]

if i can add to this one a bit..and all the advice is good so far..if the sand is hard, it's not going to filter anything ..or it may be partially hard..but to the point you don't want to go poking a stick in there as you could wreck the vanes inside..but you should be able to easily poke a finger around our 2 fingers and run sand between your fingers anywhere you can reach in the filter if it's good. i believe sand in filters is supposed to be good about 5 years..that maybe rated based on year round use as my sand is at least 7 years old and was still completely "sandy" consistency at the end of last season.

[tribe_fan]

If it aint broke - don't fix it !

I think I'd wait til the end of the season - you may damage an o ring or a gasket. It's easier to look for parts when you don't need them right away.

When you say you dont see anything in the glass - you do see water in there when backwashing ?

[aquarium]

Heh, too late.

I opened it up and there was about a half inch of grey fluffy gunk on top of the sand. I scooped out as much of that as I could. Then I dug around in the sand and determined that it was compacted, mostly against the sides and into the tank about 4-5 inches. So I used my hand to uncompact it, then backwashed. Then opened it again and stirred it some more, then backwashed. The pool has to refill now before I might backwash it again before setting it to filter.

I am SO glad I looked at the spider gasket in the multi-port valve a few days ago. It was a gooey mess and had to be replaced. Earlier in the year when I did a complete draindown, I wondered why so much water kept coming back into the pool through the return nozzles, even though it was set to pump to waste. Had I not replaced the spider gasket, a lot of that grey gunk would have gone into the pool today.

EDIT: The glass has always been clear water, until today's cleaning.

EDIT2: Opened it a third time, stirred the sand and backwashed. Pretty sure I'll still get a cloud of grey water when it's set to filter, so I'll do that later tonight. When nobody is looking.

[duraleigh]

Very interesting. What are your thoughts are on why it was compacted?

It seems to me regular backwashing should prevent that. Do you think the "grey junk" could have been from not backwashing frequently enough? Have you owned the filter since it was new?

Oops, just reread your first post. I wonder if the old owner thought backwashing was something he and the wife did in the shower?

[aquarium]

Why was it compacted? Dunno, maybe that's just what it does eventually? Probably was never properly backwashed in its early years.

I went ahead and turned it to filter, no grey cloud into the pool, so that's good.

Before I replaced the spider gasket the system ran at about 12psi, because it was leaking water around the gasket. With the new gasket but before cleaning the sand, it jumped up to 18psi. Now with the sand cleaned it's running at 15psi.

TW

[aquarium]

Been running it 24/7 the last three days as I do the alkalinity adjustment thang. Stop and backwash each day for a minute or so, get a short burst of grey water each time, so that seems to be working better.

One other thing that struck me about the compacted sand - Since the spider gasket was blown the path of least resistance during a backwash might have been to bypass the filter, so even when set to backwash there was little actual effect.

TW

[matt4x4]

I believe you got it right there with the path of least resistance - it just went to bypass.
WRT the sand compacting, I believe this happens because many people don't know better or ignore recommendations, however, most pool owners i know are adding all their chemicals through the skimmer since it is teh most "convenient" location.
Now, if you add your bleach that way, it likey will not do anything to your sand, however, floculant could easily clump your sand particles since it's designed to clump fine solids. Other chemicals may also have similar effects, algaecide comes to mind (really, why bother mixing it in a bucket first, isn't blowing it out the return pretty much the same thing?).
If sand can last 5 years+ without compacting and solidifying under noraml use, what makes 7 or 10 or 20 years so different, it has to do something with the chemicals that get put in pools.
I believe adding anything through the skimmer is going to shorten the life span of your equipment to some degree.

[Rangeball]

Matt, assuming you use bleach, do you add it through your skimmer?

If not, how?