Build up of fine green sediment at bottom of pool - possible filter problem??

[jecwells]

Hi everyone,

We moved into a house with a pool (18 months ago) and I am tearing my hair out to keep it clean and clear.

During the cooler months this is not a big issue, but currently (August) it is nigh on impossible. The symptoms are that the pool goes from sparkling clean to having a slight greeny hue and there is an increasing build up of green muck at the bottom of the pool. If I try to vacuum this, it just seemingly passes straight through the filter and the pool goes very dirty for a number of days until it all settles again. The short-term solution is to vacuum to waste, but this is very inefficient and expensive.

We have already tried a number of thing including:
- Changing the sand in the filter (now has glass media)
- Fully draining the pool and re-filling (we had very high Cynauric acid and I believed this to be the problem, but having done this 2 months ago, the issue has not improved)
- Regular testing and keeping pool in balance (I wouldn't say it is perfect, but I work hard to keep it close to perfect)
- Weekly dose of algaecide

When we had the filter media changed, it was noted that the pump is far too strong for the filter size (I don't have the output/capacity to hand) and so I have a theory that we might be suffering from "channelling" in the filter which is stopping the filter doing its job and the "dead" algae is not being removed. Last time I looked the filter pressure was quite low (less than 0.5 bar) which made me think that the water is just passing straight through with no resistance.

So questions are:

1. Does this sound like channeling could be the problem?
2. How can I diagnose this? Will it be evident if I open up the filter?
3. I was reading about adding some DE to the filter, might this help?
4. Any other ideas..!!??

To be clear, we are tenants in this house and won't be here forever so are unwilling to invest in a new (less powerful pump), but if this is the only solution then I will have to try and lobby the landlord! I would like to be (reasonably) certain that this is the issue before I go down this route.

Many thanks in advance

Cheers

James

 

[Texas Splash]

Welcome to TFP! You have algae. You need to follow the SLAM Process to remove it for good. About your questions:
1 - No (algae)
2 - Cloudy/green is algae
3 - No. DE nor algaecide will resolve algae. It's a chemical issue.
4 - SLAM Process. Be sure to test your own water with either a TF-100 or Taylor K-2006C. That's critical. Also update your signature and see mine as an example. We can walk you through this and maintain your pool the right way.

Pool Care Basics Archives

Your one-stop shop for all things TFP to include: ABCs of Water Chemistry, Recommended Chemicals/Levels, Test Kits, Troubleshooting, and much more!

www.troublefreepool.com

 

[Texas Splash]

Also check for a message I sent you.

 

[jecwells]

Hi,

Many thanks for this.

The reason I suspected it might be a filter problem is that, if left undisturbed, all the muck/sediment sinks to the bottom and (I had read, perhaps incorrectly) that it is only the dead algae that sinks.

Is this incorrect?

 

[jecwells]

Oh, and the fact that the filter pressure is so low.

 

[Texas Splash]

Dead algae will be more grey or white in color. It will be very light at the bottom and easily disturbed.

 

[Texas Splash]

A major challenge for you is that it may be difficult for you to obtain one of the recommended test kits we use here in the States (TF-100 or Taylor K-2006C). It would be ideal if you have one of those to properly monitor levels. That is very important to perform the SLAM Process in its entirety. The filter pressure may not be increasing because algae and junk is settled. That or the gauge could be faulty. But to follow our SLAM advice you really do need one of those test kits.

 

[jecwells]

Hi, thanks for all the help. We have been away for holidays and haven't had a chance to start the SLAM process yet.

As a triple-check of your theory, having not done anything in particular to the pool (ie, no SLAM, just maintaining current balance) and having been away for a week (so there has been no disturbance to the pool), we have returned from holiday and found a cristal clear pool, but with lots of sediment at the bottom (see pics at bottom).

I have cleared the sediment by vacuuming to waste, if I try to use the filter then the sediment just recirculates and the pool goes cloudy.

Does all of this fit with your original theory?

Many thanks

James

 

[Texas Splash]

Most important question .... where does someone already in Barcelona go for vacation. Ha ha

Hard to tell from the pics if that is green algae or just dust that has blown in. If you try to capture some if it you might be able to tell. Algae will just disintegrate while you should be to capture some dirt with your fingers/hands, especially if it's gritty. Since you don't have a precise test kit, go ahead and vacuum it all out to waste once you're done with that test and monitor the FC level as best as you can.

Earlier you mentioned the glass media. We're not a fan, although we do have member who use it. I'm wondering if it's struggling to do its job. That's something to watch as well.

 

[jecwells]

Ha Ha, very good question....the answer is Mallorca!!

I'm pretty sure the sediment is algae, there is a thin build up of it all over the pool and then the collections that can be seen in the photo are where the circulating water tends to cause it to gather.

I will certainly be monitoring closely, but I have been here before and I'm pretty sure I know how the story ends!

Thanks once again

 

[Texas Splash]

the answer is Mallorc

I had to Google that one. Looks great.

SLAM Process