Flow Problem

[PRB]

I have a Hayward Perflex EC75 filter and a Superpump 2 HP pump. The pump is new, replacing a 1.5 HP pump. My inground pool has 30,000 gal. I get good flow into the pool for about 15 minutes, then it drops almost to nothing. I've completely cleaned the filter. The poor flow happens with the filter has no diatomaceous earth or has the correct amount. There shouldn't be anything clogging the inflow or outflow, and if there was it seems I wouldn't get good flow at all as opposed to poor flow only after 10-15 minutes. The pressure in the filter builds up quickly and is likely limiting the flow rate. Bumping the filter helps only briefly. It doesn't seem like the air release valve on top of the filter would be an issue, as it probably is functioning fine and any air likely would just get pumped into the pool anyway. The pool water is dirty (I am just opening the pool now and am still killing algae); would this lead to pressure buildup in the filter (it doesn't seem like it, as the filter is clean). I had similar problems with the 1.5 HP pump, and thought that a stronger pump might help (it didn't). Any thoughts or suggestions?

[Bleach=Chlorine?]

This could be a filter problem or more likely, the algea is just clogging up your filter. When the flow drops does the pressure on your DE filter climb? I would backwash frequently (5-8 psi rise) and vacuum to waste if there is a lot of sediment. Do you have a multiport valve? If so, bypass the filter and the flow should not 'fall off' at all (if you need to leave and want to keep water circulating but not risk pump/filter failure from backpressure).

[ChuckD]

I have a Hayward Perflex EC75 filter and a Superpump 2 HP pump. The pump is new, replacing a 1.5 HP pump. My inground pool has 30,000 gal. I get good flow into the pool for about 15 minutes, then it drops almost to nothing. I've completely cleaned the filter. The poor flow happens with the filter has no diatomaceous earth or has the correct amount. There shouldn't be anything clogging the inflow or outflow, and if there was it seems I wouldn't get good flow at all as opposed to poor flow only after 10-15 minutes. The pressure in the filter builds up quickly and is likely limiting the flow rate. Bumping the filter helps only briefly. It doesn't seem like the air release valve on top of the filter would be an issue, as it probably is functioning fine and any air likely would just get pumped into the pool anyway. The pool water is dirty (I am just opening the pool now and am still killing algae); would this lead to pressure buildup in the filter (it doesn't seem like it, as the filter is clean). I had similar problems with the 1.5 HP pump, and thought that a stronger pump might help (it didn't). Any thoughts or suggestions?

I have the EC-65.
I'm pretty sure you have some restriction on the suction side. First thing that comes to mind is, can you see the main drain and that there're no leaves or other debris piled up on it? Happened to me until I could see the drain, and what was happening. Same symptomes. Likewise are your skimmer baskets clean?

The next thing that comes to mind is your comment about recently upping the pump's hp. What size are your lines? 1-1/2" plus head losses along the way may be adding up to the restriction killing your prime with the new pump.

How old are your valves in those lines? I had a recurring problemn with losing prime last summer because the three-way attached to the pump basket turned out to be really poorly designed for efficient flow. I replaced it with a Jandy and it made a huge difference.

Chuck

[duraleigh]

I'm not a DE expert but this identical issue has posted on the forum before.

The pressure in the filter builds up quickly and is likely limiting the flow rate. Bumping the filter helps only briefly

Algae is clogging your filter. The other posters solution was to simply clean it each time the pressure builds.....those intervals will get longer and longer as you clear your pool of algae.

[ChuckD]

Nor am I, but I've babysitted one for a little more than year now. I respectfully disagree.

I've found these filters to be very tolerant to DE build up in terms of restricting flow. More often than not, for me, it was something on the suction side holding the flow back.

C.

[CarlD]

Ok, and your basic premise is incorrect:

I had similar problems with the 1.5 HP pump, and thought that a stronger pump might help

In fact, it possibly made everything worse. I suspect you now have too big a pump for your filter.

[mas985]

It is very easy to determine a suction side restriction flow or return side restricting flow.

If your filter PSI drops as flow drops, then the restriction is before the filter (suction side or pump). If your filter PSI rises as flow drops, then the restriction is after the filter or the filter itself.

[ChuckD]

Indeed.
My 3/4 hp SuperPump will sometimes slow to a crawl, then to nothing and the pressure will also drop off to almost zero. It usually happens when the the draw is loaded up, like a clogged filter basket from vacuuming, or debris around the drain combined with the flow being diverted to either (plus the 40' run from the pool to the pump). The pump goes into a cavitation condition for which the only solution is to shut it off and turn it back on again. Clearing the obstruction allows me to continue vacuuming, or the drain to keep flowing, without interruption.

OP states the pressure jumps up when he starts. So does mine, so do they all. But jumps up to what? He also states it happens whether there's DE or not and that he's completely cleaned the filter. The question then is: when the flow slows, does the pressure drop off as well? Remembering the pressure reading is the backup of water the pump is trying to push through the filter medium, this would clearly indicate the pump is being starved to the point of cavitation, the operative being 'starved'. And cavitation doesn't occur immediately, it can creep up over five to fifteen minutes This, to me clearly indicates a partial obstruction somewhere on the suction side.

Of course if the pressure is maintained as flow drops off, then nevermind.
: )

To CarlD's point: I think it's more the pump is too big for the amount of water capable of being supplied to it. It can't overcome the losses on the suction side, and cavitates. I'm betting he has 1- 1/2" lines.

C.