Algae shoots through the filter

I'm new here, so I'm not sure if its preferred every subject gets a new thread, or if I have a similar issue if I post within someone else thread?

We've had this pool for 2 months ( its a recently purchased house ) and are just getting our feet wet. It has a Hayward ST180 sand filter and Hayward 3/4HP pump on a 4' deep, 18x32 pool. Upon removing the cover we found a swamp of leaves had gone through a hole in the cover. I cleaned it all out and after a standard volume shock failed, I went with the high Algae recommendation. That cleared the pool up but as was expected, the dead algae fell to the bottom as a white powder all over the pool. What I didn't expect was the pump/sand to just shoot the stuff right back into the pool. As soon as I'm vacuuming I see if flying back out the jet. I've backwashed the filter a few times and it is catching *some*, as the overall level is down and milky white water is coming out at each backwash, but it just seems like its not really working as well as it should.

I've tried adding the clarifier to the skimmer to catch smaller particles with no luck. At this point I'm vacuuming every 2 days, 1 hour to cover what I can see before it clouds over, then a day and a half waiting for it to settle clear so I can see what I'm doing again. At this point I was tempted just to buy an Intex pump/cartridge combo from Walmart strictly for a vacuuming device to try and finish this off.

Is this par for the course with algae? I mean I had a TON on the bottom after the shock as the pool really was a swamp.

Just starting out on the pool scene, but as its already 35C here I'm anxious to get in as the chemical balance is great.

I believe that filter is Hayward S180T with a top mount Multiport valve. If so: you could vacuum to waste, bypassing the filter and send the junk from the bottom out the backwash line.

You probably also have some trouble with your filter, perhaps the sand has been washed away. That 18" filter isn't very big and may be losing sand withevery backwash.

Is it convenient to open the filter to inspect the sand bed? The sand should be withing 6" of the top of the filter tank.

Another possibility is losing sand into the pool because of cracked lateralls or multiport valve trouble. Is there sand in the pool?

Can you vacuum to waste perhaps? Dead algae is hard to filter. Have you checked your filter to make sure you have enough sand in there? Your pump may be a little too much pump for your filter and blowing everything right on through...

Sorry...looks like I posted at same time as Dave did, listen to him not me :)

The Hayward does have that multiport valve so I was thinking of that, but it chews through water pretty fast, and our well is a low producer so I can't replace it as fast as its leaving. On top of that the pool is no longer level, so I can only overfill about 2" which buys me about 3-4 mins of backwash/vacuum action.

The pool was purchased in 1998 with this filter and pump combo, so maybe it is due. Not knowing the setup I crawled under the deck ( the pool has a deck built around it ) to put the head on the Hayward and there was no room to look inside once the plastic they had clamped in was off. I only later found they built a trap door in the deck so I can operate it from above. I'll have to check it out but I need to buy a plug for the skimmer and jet so water isn't flying out when I'm working on it. Its all about 4" below the bottom of the pool level so even with no pump powered on backwash water comes out at a decent rate so I imagine pulling the head off would result in some water flow. I don't see any sand on the pool bottom, only dead Algae.

Will a cartridge filter be better at it than sand? The 1000gph Intex cartridge/pump is only $68 here at walmart which seems fairly reasonable for a vacuum only setup that I can change easily when clogged.

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Originally Posted by ryankenn

Is this par for the course with algae? I mean I had a TON on the bottom after the shock as the pool really was a swamp.

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It's very common with undersized filters and oversized pumps, as are commonly installed as they have been on your pool.

1. Do NOT let the stuff 'shoot' through the filter. We're beginning to suspect that doing so grinds the particles even smaller.
2. If you have a valve, and any way to SLOW the flow through your filter, do so. Once you've done so, see if dirt STILL blows through your filter.
3. If dirt still does go through, it's probably time to open your filter and see if you need to add sand. Under sized filters combined with over sized pumps tends to result in sand loss at each backwash. If you do need to add sand, you will also need to add a valve between the pump and the filter, to allow you to restrict flow.

Generally, people come here wanting solutions to THEIR pool problem, and are not asking general questions. Since pools vary, we try to keep threads separate.

OK. This was sort of a general problem, so for future specifics I'll repost. Is there a calculator for pump/pool/filter sizing? It seems from my searches on this subject it has been broached many times that perhaps the pump is oversized for the filter and streaming dirt through.

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Originally Posted by ryankenn

The Hayward does have that multiport valve so I was thinking of that, but it chews through water pretty fast, and our well is a low producer so I can't replace it as fast as its leaving.

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Will a cartridge filter be better at it than sand? The 1000gph Intex cartridge/pump is only $68 here at walmart which seems fairly reasonable for a vacuum only setup that I can change easily when clogged.

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Given your water supply problem, a cartridge filter would be a much better choice. But the Intex would NOT be; the Intex cartridges are not very high quality, and would likely reproduce your problem. Also, you have a pool that's approximately 14,000 gallons, which means you're looking for a filter capable of filtering at least 1750 GPH or 30 GPM.

If you are looking for the lowest cost option, you might want to look at this filter:

Intex 56633EG 2500-Gallon Filter Pump AC 110 to 120-Volt @ Amazon

but use TWO Unicel cartridges instead of the Intex OEM 'B' cartridges:

Unicel C-5315 Replacement Filter Cartridge for 15 Square Foot Intex B Filter @ Amazon

You'd want to keep one of the cartridges in the cleaning solution, while the other was in the filter.

With the Unicel, you may get pretty good performance with clean water, but you won't get very fast cleanup. GOOD performance comes when your filter is loaded at 0.4gpm/sft, instead of 2 gpm/sft as the Intex unit above is. That would me a 100 - 120 sft cartridge filter, like this one:

Hayward C1200 Star-Clear Plus 120-Square-Foot 1-1/2-Inch Pipe Pool Filter

Or, if you want to cut costs, but get closer to optimal performance than the Intex system can achieve:

Star-Clear Plus Cartridge Filter 90 sft

I'd really like to see the EXACT make / model on your pump (not: the pump motor) to make sure of a match, however.

I crawled under there and was surprised to find its a 1HP unit. The model on the motor and pump is SP2175X10CSA, the motor rating is listed at 1HP and 11.6A.

While the size of the pump is oversized for the sand filter, is it appropriate for the size of the pool, ie. I should change out the filter OR is it too large for my application and I should downsize the pump. To be honest its not sounding that great ( I work for a residential pumps and water treatment company here ) and I'm sure its bearings are about done so if I had to replace it with a smaller model it wouldn't be a surprise. If I have to upsize the sand filter, the cartridge for the whole pool may be good.

Now that I'm starting down the path I can already see that by nature the operating requirements of the sand filter will not aide my overall well supply situation. If I can move to a decent cartridge filter for the whole pool and avoid the water loss associated with a backwash/rinse etc of the sand filter that may be the smarter move.

Thanks for the thread and the help. I know about the water chemistry but the pool flow requirements are all foreign to me and I'm trying to adapt. I'm used to 10gpm and 5um filter talk.