I'm very confused!!!!! My pool is coming with a 2 HP 2 speed 150 sq ft cartridge filter. My pool guy says if we get smaller pump & larger filter we will not have "crystal water clarity" and that a $100-200 savings is not worth the frustration of an undersized unit. I need to know exactly what size of both to get. What is the best to get the job done well. Will what I have be ok? Will it be save me money being a 2 speed.
Please help me.

Hi, I addressed this a little in the other thread. Many people think bigger is better but when it comes to pumps it is not. You want to be able to turn over the water in a reasonable amount of time, 4-8 hours is what most folks shoot for. Also, slower moving water filters better. Think of it this way, when you wash a car at one of those coin operated car washes, you are using a power washer to clean the car. The force of the water blasts the dirt off the surface of the car. Water in the pool doesn't need to be blasted to be cleaned. It needs to be filtered.
When you filter something, such as when you brew coffee, you are allowing a steady stream of water to seep through a bed of grounds and a barrier that separates the (source) water from the (filtrate) coffee. If you blasted the water through the coffee maker you would end up with watery, nasty coffee containing likely more than just a few grounds. Blasting the water through compromised the barrier, allowing grounds to escape, and the water did not stay in the bed of grounds long enough to absorb enough material to become coffee.

So, if your pump is moving water too fast with too much force, over time it will compromise the barrier (sand latterals, DE grids, or cartridge) allowing dirt to pass through, and the water will not stay in the bed (sand, DE, or cartridge fabric) long enough for the finer dirt to be "caught".

We usually recommend the largest filter you can afford and the smallest pump with enough ooomph to do the job. You could reasonably go for a 3/4hp 2 speed pump and have enough power to run a vacuum. 1 hp 2 speeds are easier to find and should work just as well as the 2 hp he wants to sell you. You just want a clean pool, not a river ride!

To be more technical, look at the gallons per minute (gpm) rate of the pump and the filter. You never want the pump to have a higher gpm than the filter. If you can give us the brand and model of the pump we can help you figure out if what the builder is recommending is a good match.

Edit: You may want to review the info in this thread. It is much more precise than I could ever hope to be!

Having a pump that is too big only has one significant disadvantage, it costs more to run. That can really add up, especially if the pump is significantly oversized, as a 2 HP pump is for that pool. There are also secondary problems, though they are less common. An oversized pump can actually damage a small filter, but that is relatively unlikely to happen. A larger pump will make the filter filter less well, it will work and the difference isn't huge, but filters always filter better when the pump is smaller. There is a limit to this process for DE filters. The pump does need to be large enough to coat the grids with DE, but that is almost never an issue.

Generally, all but the largest pools without any water features or in-floor cleaning systems or fountains will be fine with a high efficiency 1/2 HP full rated pump. For max rated or lower efficiency you may need a 3/4 HP pump.

A 2 HP pump on low speed is 1/2 HP, so acceptable. Better yet would be a 1 HP full rated run on low speed, or 1/4 HP on low speed. 1/4 HP isn't enough to vacuum, but you have high speed for that. 1/4 HP is more than enough to keep the pool sparkling clean.

It is a Hayward Filter System that is labeled a 150 sq ft. filter with a 2.0 2 speed Matrix pump. the pool guy said the pump runs 50 gpm with a cartridge filter. If that helps? I don't think they even sell a smaller 2 speed pump, we are getting the pool up north, even the pool places around town dont sell them!! where would i get them from?

Online is a great source...I'm 70 miles north of NYC with a 0.5hp pump and a 250lb sand filter (surrounded by 60-80ft high trees)...as for water clarity a picture says a 1,000 words...see below. 2HP is way too much pump for the filter they are supplying you with, but given it's a 2speed, you should still be OK running it on low all of the time. I think i have provided you multiple links in past posts as to why PS's do this, but ultimately you will have to decide who's advice you will trust

IMO, they below water does not look murky at all...sorry about the leaf at the bottom of the stairs

Can we add a timer to the pump?

You can add either a simple plug in timer if you are running the pump off a power cord or if you are hard wiring the pump there are timers for that as well. As you can see on this page, you can spend anywhere from under $25 to over $200, depending on what you want it to do.

Yup, ours is an intermatic manual timer and it is actually in our basement, next to the breaker panel, with a timer bypass switch at the pump. As zea mentioned, you can also use a simple plugin, just make sure it's rated to handle the amp draw of your pump, especially if you go with the 2HP.

See if you can get a model number for the pump you were quoted.
Hayward does not list a 2 hp/2 speed in their Matrix series of above-ground pumps.
Hayward does not list any 2 hp above ground pumps???
No luck with a Google or Bing search for Hayward Matrix and 2 hp pumps.

I've asked for the model number but havent been given one.

Is a timer worth getting (we would have it hard wired in), what kind is good? I don't know how fancy they get, but i'm sure we would just need a basic one. Could we just get through our electrician? I just had him come out for an estimate on running the electrical for the pool....won't know til later today or tomorrow.....hopefully it won't be as shocking as the gas line estimate we received!!!

We have the Intermatic mechanical timers. They are simple to operate and very reliable.
Your electrician can handle this for you. Just let him know you will be purchasing a 2 speed pump and
a heat delay for the heater.

I have a 24x12 AGP and I have a Hayard Powerflo Matrix SP1593 1.5 hp pump. I just purchased an SP15922S 1hp, 2 speed pump. First, CA electricity is ridiculous so I'm looking forward to low on a 1hp pump. Second, I do think my water flow was too fast and my filter (I believe same as your set) wasn't catching fine dust that is prevalent here. Plan to make conversion this weekend or next depending on weather. Bought new pump from Amazon. Other online retailers that carried the 2 speed pump seemed shady based on reviews.

For a timer, I just picked up a timer at Home Depot that my electrician wired when he put in electric for the pool. It's water tight and I can plug the pump straight in. Could have been hard wired as well. It has notches on a dial so I can set as many zones as I want in 30 minute increments.