How To Get Rid Of Dead Algae From Bottom Of Pool?

Hi again. We've now had the pump off for a couple of days and the clumped dead algae are on the bottom. Tomorrow we're going to add a hose to the return valve and direct the water out of the pool, hopefully this will prevent the bottom getting stirred up as we hoover. We won't turn the pump/hoover on until the hoover's in place and we're all set to go. Fingers crossed this will work.

John I've sent you a photo.....eventually.

I follow your train of thought Roger, the problem in a lot of cases is the water movement in pools is really poor so it takes a long time to actually remove anything. We move into the area of water science. Filtration is a dilution principle, The first pass of the water through the filter is only around 63.2% of the water, 2 turnovers is 86.5% of the water, 3 turnovers is 95.0% of the water, 4 turnovers is 98.2% of the water, 5 turnovers is 99.3% of the water. Baring in mind that only the water close to the surface is actually going into the skimmer. If the flow/turnover rate in the pool is low because of bad system design, if it was ever designed rather than just happening. Considering people only run their pumps for 8-10-12 hours a lot of them are only filtering 70-80% of their water and in the shut down state dirt continues to enter the pool so they seldom get a really clean pool.

Faced with that people add the flocculent to hurry things up but the pool industry does not know how to add flocculent or doesn't care. If you flocc then run the pumps as the floccs go through the pump they get all smashed up again which allows them to pass through a lot of filters. switching off the system allows the floccs to sink and be hoovered out but they cloud the pool unless you are really gentle when moving the vacuum head. The correct way to add flocculent is after the pump and before the filter, this requires a mixing process and a reasonable length of time for the flocc to form. That way you use around a 1/5th of the flocculent but get far better results.

This is why the water flow system of a pool should be designed by someone who understands and knows hydraulics and water treatment and not by a block laying gardener/general builder.

People run their pumps for too shorter time because of the cost, that area has now been addressed and so running a pump 24 hours a day cost's about the same as a conventional setup running for only 2 hours. The cost savings will pay for the additional changes and go on to save a considerable amount of money but also produce far better water quality and less maintenance time.

Ah ha spotted this after my previous post.

Can you adjust the return jet direction temporarily (it should swivel) so it doesn't disturb the bottom? I note you used the word return (singular) that's a large pool for a single return if it's correct. If you have valves on the system, partially closing the return line (gently!!) to restrict the flow a bit whilst hoovering may help. This will increase the pressure gauge reading but make sure it's not above 2 bar on the gauge.

You could do with testing the cyanuric acid stabiliser level as well because you had algae and therefore needed to choc the pool that level is important as it can play havoc with chlorine's ability to work well and keep your pool clear.

Send me a picture of your pool please, john@le-pre.co.uk

SssJust a thought, but if the pump jets keep the solids (dead algae) in suspension while the pump is running why is your filter not removing them? Perhaps all you need to do is leave the pump running for a while and if the only water exit from your pool is the skimmer then perhaps leaving the hoover connected overnight and in the bottom of the pool might be beneficial?