Gold Key fiberglass pool plumbing and pump questions

[Anonymous European in Florida]

Hi,

it's been 7 months since my fiancée bought our beautiful 1979 house and I have been taking care of the pool (my first). Balancing works pretty well and I've gotten the hang of it quickly. My questions will be about the plumbing and the pump.

Here's a quick run-down of my setup: about 10,000 gallon Gold Key fiberglass pool, 1.5" piping, Sta-Rite Dura Glas pump w/ 1HP marathon motor, Hayward C900 filter w/ brand new Unicel filter, Hayward CL220 offline chlorine feeder.

Now, the Gold Key pool has one jet (at the low end slightly to the side), one main drain and one skimmer (at the deep end). The skimmer's sump is rather large (no strainer) and has the main drain connected through the side wall of the skimmer. There's a really good picture of such a configuration here: http://www.floridamemory.com/items/show/246602 - it looks just like what our pool should look like if you took it out of the ground.

My first question is about the main drain connection in the skimmer sump: This has been plugged since the start, which I noticed just recently. I opened it and if Iapply suction there's a lot of dirt coming out, but it seems to be working. So, I was wondering if I should look into it more (and how) or just not bother with it and make very sure the water level doesn't go too low in winter so the skimmer won't run dry.

The next question is about the pump. Since I recently changed the filter cartridge (the old one started falling apart and I had to clean it almost daily) I've had plenty of suction and water-flow. The water filter shows 16psi, with the old filter the best I got was 18 after a thorough cleaning. Don't know if that matters, but I also have a replacement for the worn O-ring on the pump's strainer basket ordered. That currently leaks when I turn the pump off. The distance between skimmer and pump is about 35 feet, so I am assuming 40 feet of head. With that number the pump is rated at almost 70 gpm, while we only need around 21 (for an 8-hour turnover). So, I started looking into possibly replacing the pump with something using less energy. However, with that kind of TDH, I am unsure if I can even use a dual or variable speed pump, because all their low speed ratings go up to only 15 or 20 feet of head. Also, I want to make sure I am getting those numbers right and don't end up getting too small of a pump in the end. Right now I am running the pump 6 hours per day (down from 7.30) and would be more than willing to replace it if I can break even on the cost within 1-3 years (so, I am guessing up to $600 or $650).

Any advice is greatly appreciated.

Thanks,
Stefan

[Anonymous European in Florida]

Just found out that TDH reduces dramatically with lower flow rates, so I guess I should be okay with a dual/variable speed pump.

[PoolDoc]

Ok.

I'll do things bit by bit.

1. A 6 hour equivalent volume turnover is standard for commercial pools; 8 hours for residential. For your pool, 28 GPM gives you a 6 hour turn over (28gpm x 6hr x 60m = 10,800gal). Coupled with an adequate filter, 6 hour turnover will proved excellent water quality.

2. If this is your filter (90sft Star-Clear Plus Cartridge Filter), then 30 gpm is an ideal flow rate for high water quality, and long cartridge life. Cartridge life and performance is a function of (a) low enough flow, (b) cartridge quality, & (c) proper cleaning. This page covers how to clean a cartridge. And this is probably the correct replacement cartridge: Unicel C-8409 Replacement Filter Cartridge for 90 Square Foot Hayward CX900RE. If you can find a Filbur brand cartridge, that would also be OK. Avoid Pleatco and all Asian made cartridges.

3. Given the flow requirements of 30 gpm or less, a 2 speed 3/4 HP pump would be idea, but they are hard to find. If your existing pump is in good shape, you might want to install this motor on the pump, with a speed toggle switch. You'd be able to run it on low, except when vacuuming.
http://www.a1poolparts.com/-strse-23...eed/Detail.bok

If you wish to replace the pump, this one would be ideal:
http://www.a1poolparts.com/-strse-18...ent/Detail.bok

Since you are in Florida, a multi-speed pump is probably a bad idea. The electronics do not mix with with lightning strikes, and the costs of repairing the electronics seems to 75% of more of the cost of a new pump. A 2-speed pump will give you most of the savings, and much better life.

4. TDH -- Total Dynamic Head -- is a function of the resistance to flow due to pipe and valve friction. Although elevation changes come into play, they are not a major factor. Whether length is a factor, depends on flow and pipe diamenter. The TDH of 100' of 6" pipe at 30 GPM would be almost nil; with 1" pipe, it would be very high.
Here's more info: http://www.poolforum.com/pf2/showthread.php?5890

Good luck!

[Anonymous European in Florida]

Ben, thank you so much for the detailed reply. It's very helpful and confirmed most of my research. I am going for an AO Smith B2980 pump motor on the existing pump. I'll let you know how it goes.

The only remaining question is about the main drain. Do you think I should open up the plug and look into it further (what would the next steps be?) or just let it be and keep it plugged?

Thanks,
Stefan

[PoolDoc]

Pools run better with a main drain, so if you can fix it without too much work, I would do so. Just be careful not to do something that won't let you 'back up' if it turns out the drain can't be easily restored.