Pump too big for pool, read some posts on reducing flow with ball valve

[nicole12]

I've read some posts on a temp. solution to restricting flow for a pump that's too big for a filter, but there are different views on where to place that shut-off. I have a ball valve coming from the skimmer to the pump, could I shut some of the water off at that point or do I need to install another ball valve at a different location.

I have an Astralpool 1.5hp single speed pump and a 150lb AstralPool Sand filter. I believe my filter says 35-60gpms and from I've read on the info for the pump could be anywhere 98-30gpms depending on the feet of head, which I have no idea what that means. Pool is only around 7500 gallons. Don't know why they set me up with such a high powered filter but at this point I don't want to spend the money on a new pump.

[Waterworks]

Never shut off a valve in front of the pump with the pump running. This will cause the pump to catch air or cavitate, which causes problems. If you want to reduce the flow going to your sand filter, put the valve between the pump and filter. This allows you to shut the valve and slow the water going into the filter. This can also be a bad idea if you end up making your pump work outside its efficiency curve. It would be difficult (read: nearly impossible) for you to tell when you are in and when you are out of the proper curve. I wouldn't worry too much about that though, just don't shut the valve much past half way.

Brad
www.waterworkspools.com

[cschmelz]

I've read some posts on a temp. solution to restricting flow for a pump that's too big for a filter, but there are different views on where to place that shut-off. I have a ball valve coming from the skimmer to the pump, could I shut some of the water off at that point or do I need to install another ball valve at a different location.

I have an Astralpool 1.5hp single speed pump and a 150lb AstralPool Sand filter. I believe my filter says 35-60gpms and from I've read on the info for the pump could be anywhere 98-30gpms depending on the feet of head, which I have no idea what that means. Pool is only around 7500 gallons. Don't know why they set me up with such a high powered filter but at this point I don't want to spend the money on a new pump.

Actually the ball valve WOULD solve the problem (eventually) as it would lead your pump to a VERY early grave and then you could put in a nice 0.5hp or so pump to solve the problem....

[mas985]

Nicole,

Actually, you can put the valve at anypoint after the pump. Head loss is additive and does not really matter where it occurs. Any restriction affects the entire flow path GPM so find an easy place to put it in the return path. However, if you place it after the filter, you can more easily adjust the flow by watching the filter PSI rise. You do not need to worry about pump damage as long as you keep the PSI rise to less than 10 and the total rise to less than pump maximum, usually 35 PSI but I would not exceed 25 PSI. Note that the restriction PSI is similar to puting solar in.

[eljefe281]

nicole,

I don't know how much you pay for electricity, but I'm guessing that it's not cheap up there in MA.

Considering the cost of the new valve being talked about and the unnecessary horsepower being used, you'll probably be money ahead if you replace the pump now.

Of course, cash availability is always a consideration...

[cleancloths]

When you throttle a pump on the discharge you lower its HP draw as well.

[Poconos]

Actually what is happening when you restrict the flow on the output side of the pump is to increase the pressure, reduce the flow, and thus reduce the work that the pump has to supply. The reduced work load, i.e. moving water, results in a slight decrease in power consumption. Opposite to what may seem intuitive. These comments apply to centrifugal pumps only, which all pool pumps are as far as I know. I agree that in the long run the cheapest option is to replace the pump.
Al

[nicole12]

Thanks for all the response. If I do go with a new pump 1/2hp should be sufficient? The filter says 35-40gpm. I think right now the pump is putting in around 80gpm. Does the pump need to be the same brand as the filter?

I bought this whole pool, filter, pump from a pool store and we installed ourselves. Not sure why they would give such a high powered pump for our size pool and size filter.

Based on info on this forum I calculated the turnover rate for my pool is around 1.6hrs and I run the filter 3hrs in the am and 3hrs in the pm. Can I cut that down a little bit to save some energy consumption?

[Poconos]

You can mix and match any components you want. Why they sold such a big pump? They made more $$$ and they could have been stupid. In my opinion there is no magic number for the number of water turnovers in a day. I'd say run it as little as necessary to keep the water clean and sanitized, read...keeping the chlorine mixed well. Trial and error is your best option. Again, in my opinion...others have different thoughts and advice.
Al

[mas985]

Nicole,

Before you go out and spend money on a pump replacement, is your pump and filter a matched unit? Some of Astral pool products are and they do have a matched unit of a 1.5 HP pump and 150 lbs filter so I suspect that it is a matched unit. If so, it would seem unlikely that they would pair a pump with a filter that would cause damage. So you may not need to replace the pump.

Also, is this for an above ground pool? What is your pressure guage on the filter currently reading? From this you can determine the feet of head your current pump is experiencing and then more accurately calculate the GPM.

If you do decide on a new pump, with 7500 gallons, you need only need 16 GPM for an 8 hour turnover. Not much at all. You could use the smallest pump available (1/2 HP) or better yet a two speed pump and operate on low speed most of the time. Even most 1/2 HP pumps will provide more than 40 GPM between 45-65 feet of head so it may be better to go with a two speed pump.