So, we have a 1700 gallon pool that was stricken with algae, and our neighbors have one about twice that size that got hit at the same time. We both shocked our pools and used an algicide that drew all of the algae to the bottom in clumps. This was great - the water was clear again. However, neither of our vacuums are working to clear up the clumps of algae at the bottom.

We have a vacuum that connects to our filter, they have a vacuum where you attach a hose and it pushes water through a filter bag on the other side. In both cases, the algae just ends up circulating and clouding the pool again until we leave it alone and it all settles at the bottom again.

Our filters are doing the same work, roughly, insomuch as it's catching algae, but needs to be cleaned constantly and is not circulating enough to really clean it up (the algae was cleared almost two weeks ago now).

So, are there any tips out there on how to get it out short of emptying the pool, cleaning it, and refilling it? If we go that route, pool season is over for this year.


  • What about a wet/dry shop vac to pull the bulk of the algae settled onto the bottom into a container that can be easily dumped? – bib Aug 24 '15 at 22:00
  • When's the last time you backwashed your filter (or whatever its equivalent is)? Have you doublechecked the valve settings? This sounds like the filter is either being bypassed or isn't doing its job. – keshlam Aug 24 '15 at 22:22
  • With this type of filter you simply remove the filter and clean it. This needs to be done often for this particular issue. The filter is sized properly for the pool, but none of it is high-end pool equipment in this case. The filter does filter it out when it gets there, but it doesn't have enough flow to pull stuff up from the bottom (most filters don't). – Jesse Williams Aug 24 '15 at 23:02

When you added the algaecide it contained a flocing agent which clumps up the dead algae which it then settles to the bottom of the pool.

Filters do not filter out dead algae and all you're doing is recirculating the dead algae.

How to Fix

  1. Some pool owners will need to fill their pool up with water in order to proceed to the next step. You may not.
  2. The multiport valve on your filter may have a Waste option. Use it to blow out the dead algae while you vacuum. Do no use the backwash option, only the Waste is needed.
  3. After you have blown out the dead algae, then you will probably need to tap off your pool again, then backwash and rinse.

If the multiport valve doesn't have a WASTE option, then you will probably need to consider purchasing an external pump and attach it to the vacuum to blow out the dead algae into your garden.

  • 1
    Since he has a cartridge filter, there is no multiport valve. But all is not lost. Most cartridge filters have a inlet that is sized for a standard pool hose. Just take off the top of the filter, remove the filter cartridge and then stick a extra pool hose into the inlet (usually bottom center of the housing) and either pump to your lawn or your sewer waste. – diceless Aug 25 '15 at 5:02
  • @diceless thanks. I did not know that about cartridge filters. – Kris Aug 25 '15 at 12:55
  • I've accepted this answer, but must add a caveat - cartridge filters are just not good for this sort of thing. The following season we purchased an Intex sand tank filter (that does have a multiport valve). The pool did go green again at one point, but the filter took care of business. This year we upgraded our pool to a much larger one and... it went green (this is the down side to having lots of trees in the yard). I didn't think about using the WASTE and let it just cycle, then backwashed it. It's beautifully crystal clear after just a few hours. Lesson: get a sand filter! – Jesse Williams Jun 26 '17 at 14:21

I am surprised that pool leaf rakes are not marketed to also be useful to clear algae clumps. However, this is the tool I'd use:

enter image description here

mounted on a pole to reach the bottom:

enter image description here

This isn't all that hard to do—maybe an hour's work—but it is very pleasant and satisfying. Certainly more of a sure kill than twiddling with the filter system.

  • We did try this, and actually also modified one with women's pantyhose to try to have an even finer netting. This stuff just puffed through all of it like there was nothing even remotely solid about it. In the end, we just drained the pool for the year a bit early and scrubbed the heck out of it with chlorine bleach. So far this year it's been fine. – Jesse Williams Jul 23 '16 at 15:59

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