Is it dead algae, sand from the filter, or something else?

jreiser

Member
Jun 15, 2010
24
Long Island, New York, USA
We just opened the pool 12 days ago and the pool has been in swimming condition for the past few days. I've been keeping the pool at shock levels on a daily basis and find what I believe is dead algae at the bottom each day, but less and less. An overnight FC loss test will happen soon but I'm keeping FC levels up for now.

I'm running the pool 24x7 for now and have been cleaning and backwashing on about a daily basis. I'm noticing that the dead algae may be accompanied by sand or some other gritty material. This seems to be mainly around the water returns which made me wonder if it's sand from the filter, and may be indicative of a problem. The pool pro who opened the pool for us was here a couple days ago doing some other work, and he suggested that frequent backwashing can make the filter less efficient at filtering out smaller particulate matter, and we'll probably see less of this grit after a few days without backwashing.

Does that make sense? Can you really backwash too much? Unfortunately the pressure gauge on the filter is shot, but we're replacing that tomorrow or Tuesday. Hopefully once the gauge works I'll have a better sense of when I need to backwash, and when to resist the urge. Our waste water goes out into the street, and I think I just enjoy seeing all that murky water wash away.

Swimming today I tried to feel some of the sediment to see just what it was or at least what it felt like. Some of it goes into solution pretty much on contact and I can't say I felt anything that I could describe. I'm guessing that's the dead algae. The other stuff is gritty and felt like fine and fairly regular sand. I suppose I could take a sample and dry it out if that helps establish what it is, but if the filter can start trapping it, I guess it may not matter.

Thanks!
- Jason
 

coloeb

Well-known member
Mar 13, 2009
226
Sand filters actually do work better if they are somewhat "dirty", Backwashing should only be done when your pressure increases by the amount stated in the owners manual. For this reason its never a good idea to go very long with a broken guage.
Things I have seen that were causes of sand in the pool;
1- Wind blown dirt

2- Wrong type of sand used to refill a filter.

3- Too much sand put in a filter

4- Broken laterals

6- A broken return line. ( this one happened to me )

7- Selector valve problems on the filter.

8- Improper backwashing procedures

Hope this helps .
 

Bama Rambler

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2009
22,964
SouthWest Alabama
Coloeb gave you a good list of possibilities.

To find out if it's coming from the return partially unscrew one (or more) of the eyeballs and tie a sock over it (them) and run the pump. Check it after a while and if there's dirt/whatever in the sock it's coming from the filter.
 

jreiser

Member
Jun 15, 2010
24
Long Island, New York, USA
Bama Rambler said:
Coloeb gave you a good list of possibilities.

To find out if it's coming from the return partially unscrew one (or more) of the eyeballs and tie a sock over it (them) and run the pump. Check it after a while and if there's dirt/whatever in the sock it's coming from the filter.
Thanks for such a seemingly obvious idea! I wouldn't have thought of that.

- Jason
 

jreiser

Member
Jun 15, 2010
24
Long Island, New York, USA
coloeb said:
Sand filters actually do work better if they are somewhat "dirty", Backwashing should only be done when your pressure increases by the amount stated in the owners manual. For this reason its never a good idea to go very long with a broken guage.
Thanks! Great to have confirmation of this. It certainly makes sense intuitively but what I know about pools is what I've learned here in the last couple weeks. So it's accurate but somewhat incomplete. More reading to do!
coloeb said:
Things I have seen that were causes of sand in the pool;
1- Wind blown dirt
Not a lot of dirt to blow after we powerwashed the patio.
coloeb said:
2- Wrong type of sand used to refill a filter.

3- Too much sand put in a filter
Certainly possible. We rent the house and the owner did most of his own maintenance or had his pool guy do it... but that guy is unreachable. If this seems like a concern I'll address it with the owner.
coloeb said:
4- Broken laterals

6- A broken return line. ( this one happened to me )
Could be... harder to diagnose I would think. No air in the lines unless I do something to cause it (ie: connecting skimmer vac with a little trapped air in the hose)
coloeb said:
7- Selector valve problems on the filter.
Could a failing multi-port valve cause the issue? The valve takes nearly superhuman strength to turn. My pool guy opened it and cleaned it out, and lubricated the gasket(s). This helped quite a bit but it's still pretty tight... a lot better but not like it should be. There was quite a bit of sand visible in the works which probably shouldn't be the case.
coloeb said:
8- Improper backwashing procedures
My frequent backwashing is certainly playing a part. I just have to figure out how big a part.
coloeb said:
Hope this helps .
Tons! Thanks!

- Jason
 

waste

TFP Expert
LifeTime Supporter
Mar 29, 2007
4,160
Coastalish 'down easter'
Just to add:

Sand in the pool, not from the filter, can also come from a degrading concrete deck.

(similar to Bama's, but easier :cool: ) Leave the eyeball in and rubberband a lady's kneehigh stocking to it - check for debris after the pump runs a cycle :)

It does sound like a mixture of dead algae and sand :(

If the return line was broken, you'd be loosing a fair bit of water.
 

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