Appropriate pump size for sand filter

[greenegirl]

Hi! I have a Hayward sand filter-S244T and had a 1 1/2 hp pump. The pump went and had to replace. Tech installed 1/2 hp pump. Hayward S48H2N122B1 Is this ok?
Water looks crystal clear so far, but lots of sediment on bottom of pool.
What do you all think?

 

[mas985]

You can't really compare pumps by their label HP rating. HP ratings do not accurately predict pump performance.

Is the filter pressure higher or lower than with the old pump? If lower or equal, then the pump should be fine. If higher, that means higher flow rates which can push debris through the filter.

Do you know the model number of the old pump?

 

[greenegirl]

Hi! Thanks for your help! The pressure is lower now…was 18, now 12.
I don’t know the model # of the old Hayward pump that fried .

 

[mas985]

The lower pressure means lower flow rate and that usually means better filtering.

However, sand filters are really poor at filtering out dead algae so that may be what is on the pool floor. Try adding a little DE to the filter and then vacuuming the floor.

 

[greenegirl]

I’m new to this…can I Google how to add DE to the filter?

 

[mas985]

Try this:

Add DE to a Sand Filter

A clean pool filter will increase the efficiency of your pool! ... your filter are to backwash it, clean the manifolds and grids, and add new DE.

www.troublefreepool.com

 

[greenegirl]

You are awesome! Thank you, so much!

 

[sktn77a]

Is this ok?

Well, that's pretty unusual to replace a 1.5HP pump with a 0.5HP pump. Unless there was some compelling reason to believe that the 1.5HP pump was too big for you pool, I'm not sure I see the point of downsizing that much(?)

How big is your pool?

 

[mas985]

The reason the pump was reduced in size was due to DOE regulations. You can no longer manufacture single/dual speed pumps with HHP > 0.711.

Pump DOE Regulations - Further Reading

www.troublefreepool.com

 

[greenegirl]

Well, that's pretty unusual to replace a 1.5HP pump with a 0.5HP pump. Unless there was some compelling reason to believe that the 1.5HP pump was too big for you pool, I'm not sure I see the point of downsizing that much(?)

How big is your pool?

I have a small pool…14x28, 14,000gallons.

 

[sktn77a]

The reason the pump was reduced in size was due to DOE regulations. You can no longer manufacture single/dual speed pumps with HHP > 0.711.

Yes, but there are plenty for sale out there (amazon, ebay, usual online pool stores) with no apparent restrictions(?) Maybe just pool stores/installers won't install them?

 

[mas985]

Yes, but there are plenty for sale out there (amazon, ebay) with no apparent restrictions(?) Maybe just pool stores/installers won't install them?

Existing inventory can be sold but they have not be manufactured for 3 years now so there are not many left. Remember you cannot go by the label HP it is meaningless. Just because it is labeled at 1.5 HP doesn't mean it actually is. Most of these are SPL rated which means the actual THP is lower than the label.

The true size of a pump is determined by the head curve, not the label rating.

 

[mas985]

The following chart shows the pump motor THP vs the flow rate delivered on plumbing Curve-A. For a given, THP, you can see how large the variation in flow rate can be and the widest range is around THP of 1.5/1.65. So even THP is mostly meaningless.



Here is another way to look at the data plotting HHP (curve-c) vs THP. Note there are some pumps with a THP of 1.5/1.65 that have a HHP below 0.711 which meets the DOE criteria. There is even a 2 THP pump that meets the criteria. The motor THP only tells you the maximum HP load one can put on the motor but not what the actual impeller load is.