Pool Opening Problems.

[TheGoose]

I did backwash the filter. Extensively. I backwashed for several minutes and caught samples several times. It did take a long time for the water to clear. Then I rinsed and repeat, 2-3 times. I tried to see if any sand was coming through the backwash but I never detected much, but it was hard to disceren from all the "junk" coming out either.

When I backwash my start-up pressure is normally 17-20 psi. I added about 3/4 of a 'cup' of DE to the skimmers until the pressure reached ~1-2 psi above clean pressure. Funny thing was that I came back about 15-20 minutes later and the pressure was running ~25 psi. I then shut the filter off for a few minutes and re-started, and , voila, the pressure was back about ~21-22 psi.

What bothers me is that the filter pressure will rise, over time, running normally. I now have the pump running on low speed 24/7 hoping that under low speed the sand filter can catch the stuff that normally gets through. I have the DE in the filter, but the water is still cloudy.

I need to pull the top off next and add some sand. I'm gonna put unions in on every connection. I'm gonna start with 2 bags, unless the visible level looks low enough. Then I'm gonna put a throttle valve on the BW line and pinch it down. I checked out what the flow under low speed looks like during BW and it still does about 20-30 GPM so I could just try that too.

I will try the other DE test also but I have never seen the DE blow back into the pool but I will give it a look again.

[PoolDoc]

Ok, with a Tagelus 60D, the absolute do not exceed is 47GPM. Do NOT take that sucker off low speed. You can probably even backwash on low. (Need about 40 GPM for that).

The pressure behavior you're describing is pretty typical of DE; it re-compacts under restored flow.

Also, we've got a rash of problems like yours -- probably because so many pools got 'slimed' during the exceptionally warm spring. The good side of all this (for me) is that it's giving me a widespread pattern to look at. In EVERY case, an over-pressurized sand filter has been involved. However, in one case, we're NOT seeing what we've always presumed; that the particles would be filtered by a DE or cartridge filter. In this case, the owner cleaned up (de-greened) with sand, and then switched to a cartridge, and now STILL cannot filter the cloud.

What I think may be happening is that the high rate / high flow through the sand filter is fracturing the algae particles and they are leaving the sand filter as a stream of much finer particles than when they entered. So, what I'm asking people to try, is to raise the chlorine high enough to last a couple of days, and to then turn the pump off.

My hope is, it will settle some. If it settles enough to vacuum out on waste, then we have a solution. If not, the next step is to try a floc, and then a clarifier. But it appears that these particles may not filter out in any reasonable time, except with an over-sized (low flow per sft) DE filter --- and that would be EXPENSIVE.

The way to avoid it in the future is to NEVER allow algae to be forced through a sand or cartridge filter by an oversized pump.

[TheGoose]

I know what 50 GPM looks like and I'm certain my pump does more than 50 GPM open ended. Can't really tell what the flow would be through the filter and return piping, but if you put it to waste or backwash it's at least 50-60 GPM. I wonder if there as a flowmeter built specifically for pools I can put in-line to check the flow. Also it would be handy to know when the filter is really getting plugged instead of relying on a pressure gauge.

I sized the pump /tank going by their charts-the 60D was supposed to be good up to 60 GPM and the pump was supposed to do 50-60 GPM. What I'm finding out is that I really needed the 100D (as you suggested) to handle the flow.

If I did go back to DE ( I had an old Sta-Rite Swimquip stainless DE before) which one would you recommend? My plumbing is on top, I would prefer to stay with a top mount valve so I wouldn't have to massively modify the plumbing. But I can change it if need be.

[PoolDoc]

Yes, there's a flow meter; I've always used Blue White's meters. The others were either massively expensive, or not accurate enough.

Blue-White Flowmeter for 1-1/2" PVC Pipe, Horizontal Installation

Blue White Flow Meter manual

Regarding filters -- a sand filter will do fine, if you keep the flow in the correct range. I'm realizing I've never personally seen the sort of problems everyone is having, because whenever I took over a pool, I'd whine and fuss until I could replace the pump or the filters, OR I'd surreptitiously throttle the flow back.

This whole episode is convincing me more and more that we -- PoolForum -- really needs to shift to making specific buy this; buy that recommendations. Now that Amazon is carrying such a wide range of gear, and their indexing is stable (even if their descriptions aren't always correct) so that I can count a link EITHER going to the correct product OR dying safely. I want to work with Mark (mas985) to come up with 4 or 5 standard pump/filter/valve/layout combos so people can not only get the right chemicals and the right test kits, but also the right gear.

Case in point is the BW flow-meter I listed. Five years ago, I couldn't have done that, since the few online companies I trusted had very limited lines of gear.

It won't be perfect, but it will spare a lot of people a lot of grief. And, with the 4 - 6% commission from Amazon, it will help cover costs here.

[TheGoose]

Ben,

Looking at the 1-HP Whisperflo curve https://www.pentairpartners.com/prod...ctcatalog.aspx I'm trying to figure out what my pump is really pushing.

Taking the fact that I have 20 psi of backpressure, and 1 psi = 2.31 ft of head, then is it safe to assume that I have 46.2 ft of head, or to make it even about 50 ft of total head?

Looking at the chart on pg. 157 and going by the curve represented by "G", which is shown to be the 1-HP whisper-flo (1.65 service factor) it's showing that I should have about 90 GPM of flow.

Taking the low speed chart "B" and considering that I have about 6 psi of backpressure on the system = 13 ft of head. "B" shows at least 40-50 GPM at ~13 ft of head.

Of course I'm not counting head losses from the 2-3 ft of head losses on the suction side so it would be a little bit lower. Also consider that my return piping is 1.5" from the filter to the pool. 90 GPM is way more than the filter is designed for so that would definitely explain why it has never filtered very good.

[TheGoose]

Water is looking slightly better today. FC>5, I turned the pumps off and I'm letting it sit overnight. Tomorrow I'm gonna vac to waste and add sand to the filter.

[mas985]

Taking the fact that I have 20 psi of backpressure, and 1 psi = 2.31 ft of head, then is it safe to assume that I have 46.2 ft of head, or to make it even about 50 ft of total head?

You have to add 3' for the height of the filter gauge above the pump and as you pointed out, there is suction head as well but with 2 suction lines, it should be fairly small so I agree that the flow rate should be at most 90 GPM. Also, low speed is simply half the flow rate of high speed so you really don't need to use the low speed head curve.

[PoolDoc]

Thanks, Mark.

Goose, given that the MAX flow -- for good filtration -- through a 24" filter, like the Tagelus 60, should be 45 GPM or less . . . it's safe to say that you are (1) wasting most of the pumping electricity you are consuming and (2) forcing the filter to fail. If you have 45 GPM on low, you shouldn't even turn the pump onto high, when you backwash.