Gold Key fiberglass pool plumbing and pump questions

[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.