Matching a Pool Pump to Your Sand Filter

Sand filter listings and the flow rate

A sand filter sits between the pump and the pool. The pump pushes water through the filter, and the filter's bed of sand catches particles as the water passes. The filter holds the flow back slightly, and that resistance has a name: pressure drop. The pump overcomes that resistance every time it runs. The ENERGY STAR program page describes the pump's role the same way: re-circulating water through a filter to maintain water clarity.

A sand filter listing states a flow rate, usually in GPM (gallons per minute) or GPH (gallons per hour). Sellers state it as a range or as a maximum. The number tells you how much water the filter is designed to pass under normal conditions, not how much the pump must deliver. Reading the filter's flow figure and the pump's flow figure together is the start of a match.

The filter's tank size is stated in the title or the bullet list, often in pounds of sand. Larger tanks usually state a higher flow. The tank size is a listing word; whether a pump's flow suits a tank size is a question for the maker's sizing page. Combo listings for above ground pools pair the two by default, while inground pools usually list them separately.

Pressure drop and the PSI reading

Pressure drop is the difference in water pressure between the inlet and the outlet of the filter. Every filter resists flow to some degree; a sand filter resists more when the sand bed is deep or the media is fresh. The filter listing rarely states the pressure drop as a number. What you see instead is the pump's head in feet, which includes the filter's resistance as part of the whole system.

A filter gauge shows PSI (pounds per square inch) of pressure in the system. The PSI number is a reading on a gauge, and the maker's manual and the filter label state what it means for that model. The psi reading article explains the term in more detail.

Pump listings: flow and head together

A pump listing states two connected values: flow in GPM or GPH, and head in feet. Head is the resistance the pump can push against, expressed as the height of a column of water. A pump's flow falls as head rises. Both values appear in the listing because they describe the same performance curve.

When you read a pump listing, the stated flow is the number at a stated head. A listing that says a certain GPM is telling you flow at a certain resistance, not the maximum the pump can ever move. The flow rate article and the head article explain those units.

The filter's pressure drop is one part of the total head the pump faces. The plumbing, the height of the water and every fitting add to it. That is why a matching decision needs the whole system, and why this site does not calculate a match from pool size alone. The pump's stated horsepower is a motor figure, not a matching figure; flow and head describe what the pump does with that motor. The horsepower article explains that separation.

Pump and filter combo listings

Sellers often list a pump and a sand filter as one product, most often for above ground pools. The title states both: the pump's horsepower or flow and the filter's tank size. The seller is presenting the two as a set, and the flow values in the title are the seller's own stated numbers.

A combo title may name the pump's speed type, such as single speed or variable speed, and the filter media. Read the bullet list for the stated GPH or GPM of the pump and the stated flow range of the filter. The best sand filter pump guide compares those combos on stated details.

The filter media itself may appear in the title: sand, and sometimes alternatives such as filter balls or glass. Media words describe what goes inside the tank, not a flow promise. This site makes no claim about one media cleaning better than another; the maker's manual states what the filter accepts.

What the makers publish for sizing

Pump and filter makers publish sizing pages and calculators. Hayward, for example, offers a total dynamic head calculator on its site, a tool that estimates the resistance of a plumbing system from inputs the owner enters.

Those tools and catalog pages are the right place to confirm that a pump's stated flow and head sit inside the filter's stated range. The maker's manual is where the filter's own flow range and the pump's performance curve appear in the maker's own words. This site does not do sizing math; the maker and an installer confirm the match.

Questions to ask before you pick a pump

The questions below come from reading the listing words, not from measuring anything. Each one points to a stated figure or to the maker's own document.

• What is the sand filter's stated flow range? Read it off the filter label or the maker's manual.
• What is the pump's stated flow at the head of this system? The pump listing and its performance curve state it.
• Does the pump listing name a speed type? A variable speed pump can run at lower flows, which may suit a filter's stated range. The variable speed guide compares them.
• Which pool type does the listing name? Above ground sand filter combos and inground sand filters are separate listings. The inground pump guide and the above ground pump guide separate those.

What to pick for your situation

Questions

Do you need a pump with a higher GPM than the filter states?

No. The filter's stated flow is a range the filter is designed to pass. The pump's stated flow should sit inside that range at the head of the system. The maker's sizing page confirms it.

What is PSI on a filter gauge?

PSI stands for pounds per square inch. The gauge shows the pressure inside the filter during operation. The maker's manual and the filter label state what a normal reading is for that model.

Can any pump work with any sand filter?

A listing pairs a pump and a filter when the seller states both. Matching depends on the stated flow values and the resistance of the system. The maker's sizing page and an installer confirm a pair.

Where do you find the filter's flow rate?

The filter label, the maker's manual and the listing title all state it. Look for GPM or GPH in the filter's bullet list.

What does head mean in a pump listing?

Head is the resistance the pump can push against, expressed in feet of water column. The filter's pressure drop is part of that resistance, along with the plumbing.