Pump is shot. Shopping for replacement...

[Scrapple]

My Hayward Power-Flow LX 1hp pump is shot. The bearings are worn and noisy. I want to replace it with a 2 speed pump, cost permitting. The pump is paired with a Hayward S166T 16" sand filter. I want to drop a pump size or two as I think 1 hp may be too large. What say the board? Would 3/4 hp be a better fit?

Thanks. And my neighbors thank you too.

[Scrapple]

Anyone? Looking for some input before dropping $$$.

Thanks.

[CarlD]

Hayward doesn't make a 2spd pump small enough. Their smallest is the 1hp Superpump, and that will probably bust your filter at full power, unless you put a smaller impeller on it. I think Pentair makes a 3/4 hp 2spd but that is the smallest I know of. Too bad there's no 1/2 hp 2spd out there, AFAIK.

[BigDave]

Hayward does make a power-flo Matrix 1hp 2speed 115V. I can't tell how much you'd need to change the plumbing.

[Scrapple]

I'm noticing that I would need to buy at least 1 HP to get a 2 speed. I'm running 1 HP right now and I think it may be too big. Leaning toward the Hayward 3/4 HP. I would save a little bit with that over what I have. The current pump is 6 years old according to Hayward.

[mas985]

Technically, there is no pump on the market, except maybe an Intex, that is a correct size for your filter. Your filter has a max flow rate of 35 GPM but ideally, you should be around 21 GPM with that filter.

However, the good news is that the Power LX 1 HP pump would provide about 49 GPM on high speed and about 24 GPM on low speed. So one option would be to replace the pump motor with a 2 speed motor and operate on low speed all the time.

[Scrapple]

With the short pipe run I have, my pump can do about 60 GPM, which is pointless if the filter can only do 35. I'm stepping down the HP 2 speed or not. Thanks for the input.

[BigDave]

I think mas985 is telling you that a 2 speed motor may be the only way to get as low as you need to go.

[Scrapple]

Just ordered the 3/4 HP Hayward Matrix from Amazon. Might have to put in a new outlet. My old pump has a twist lock cord. Think the new one is standard 3-prong.

[BigDave]

Or you can change the plug. Twist-lock is code in my town. Consider plumbing in a valve between the pump outlet and the filter to throttle the flow - that's still too much pump for that filter.

[CarlD]

Twist-lock is code in my town, too, and the cord can't be more than 3' long.

[mas985]

I wish you had checked in before purchasing. The 3/4 HP matrix has close to the same flow rate as the Powerflo LX 1 HP. 48 GPM vs 49 GPM so you really are no better off. This is why it is generally a mistake to size a pump by the label HP rating. You would have been better off with a two speed on low speed.

BTW, how did you come to 60 GPM? That is much too high for that pump on such a small filter.

[Scrapple]

That is what is listed on the pump label. I will use a valve to throttle the flow rate.

At some point I will post pics of the pool to see if anyone can ID what brand it is. Came with the house, wife won't let me tear it down. I still have to fix a leak around the skimmer. It never ends.

[Scrapple]

Would this one work? Looks like the ends come off and can be threaded into the inlet.

http://www.pvcfittingsonline.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/s/k/sk-ball-valve_1_7.jpg

[BigDave]

Inlet of the filter? I don't know if it would thread directly on - you'd probably need a threaded version of that valve and a nipple.
I like ball valves for throttling. PoolDoc recommends gate valves because they're easier to operate.
Hint: When you winterize, set the ball valves to 45 degrees - water is trapped in the valve body when it's open or closed.

[mas985]

When using a throttling valve, it doesn't matter where you put it. The flow rate reduction is the same. However, you are probably better off putting it after the filter so it doesn't collect debris.

But another option is to put some DE into the filter. That will add restriction and reduce flow and improve filtering. At least this way you get something for the reduce flow rate. To get 35 GPM, you want to add enough to raise your clean filter pressure by at least 4 PSI and that should do it.

Also, flow rates on pump labels are meaningless. Those are usually run out or maximum flow rates and not what you typically get on pool plumbing.

[BigDave]

@mas985: Clever idea, DE for throttling. I suppose it would clog up real quick though.

[mas985]

Only if the pool was dirty but isn't that point.

[BigDave]

I just thought of another reason to place a throttle valve between the pump and filter: If there's too much flow on backwash, much sand will be lost.

[mas985]

If that will be an issue, it should be an issue with the existing pump as well. But a good point.