How Many Pool Skimmers Do You Need? Why Surface Area and Pump Flow Both Matter
Pool knowledge · Equipment
How Many Pool Skimmers Do You Need? Why Surface Area and Pump Flow Both Matter
Many people pick skimmers by pool size alone. A clean water surface depends on two things at once: how much surface each skimmer has to cover, and how much water actually flows through it. This guide explains the method, walks through a worked example, and compares the concrete-pool skimmers available at WinWin Pool.
What a skimmer does
A skimmer is the suction opening set into the pool wall at the waterline. It draws in the top layer of water together with leaves, insects, dust and sunscreen oils, catches them in a debris basket, and passes the water on to the pump and filter. Most dirt in a pool floats on the surface. With too few skimmers, or skimmers in the wrong place, debris collects in the corners, the water clouds faster and you end up using more chemicals.
The key rule: you need enough skimmers to cover the surface area and enough to keep each one within its flow limit. Calculate both and use the larger number.
What you need to know first
- Water surface area: length × width (m²), or the real area from the drawings for a freeform pool
- Average depth and turnover to find the required flow: pool volume (m³) ÷ turnover hours. A typical home pool uses 6 hours; busy hotel and public pools usually use less
- Flow of the pump actually chosen (m³/h), read from the pump curve at your system's head, not the maximum flow on the box, which is measured with no resistance
- Share of flow through the skimmers: if there is also a main drain, you need the measured split. If it hasn't been measured, assume 100% goes through the skimmers
- Pool type: concrete, vinyl or fibreglass (the models in this article are for concrete pools)
- Mouth style: standard, wide mouth, 600 mm surface opening, or with an extension, plus the wall details
- Site conditions: indoor or outdoor, prevailing wind, leaf load, and where the return inlets are
- Use: a private home pool or a hotel/public pool, which carry different loads and requirements
The sizing formula
A = length × width (or the real area from drawings)
# 2) Pump flow and flow through the skimmers
Q_pump ( A × average depth ) ÷ turnover hours (home pool: 6 h)
Q = flow of chosen pump × share through skimmers
# 3) Count by area and by flow (base EM0020-RC = 9 m³/h each)
N_area = round up( A ÷ 25 )
N_flow = round up( Q ÷ 9 )
# 4) Count to use
N = the largest of ( 1, N_area, N_flow )
Round up means any decimal goes up to the next whole number, for example 1.28 2 or 2.05 3. You can't buy part of a skimmer, and rounding down leaves you short.
This guide uses the EMAUX EM0020-RC as the reference model, sized at 9 m³/h per skimmer, the manufacturer's catalogue flow (150 L/min). The 25 m² per skimmer coverage figure is WinWin Pool's preliminary area criterion.
If you choose another model, change the flow divisor to suit it: the EM0010-RC and the EM0030EM0050 range can also use 9 (the EM0030EM0050 catalogue range is 912; we use the lower value), but the EM0180TS-SC and HAYWARD SP3400 must be sized at 5 m³/h, per the installation manual and the manufacturer's recommended maximum. The LASWIM PA00249C has no manufacturer rating yet, so we size it conservatively at 5 m³/h.
Worked example: an 8 × 4 m home pool with the EM0020-RC
A home pool of 8 × 4 m with an average depth of 1.5 m, sized for a 6-hour turnover (the whole pool passes through the filter once every 6 hours). The main-drain split hasn't been measured, so we assume 100% of the flow goes through the skimmers.
| Step | Calculation | Result |
|---|---|---|
| Water surface area | 8 × 4 | 32 m² |
| Water volume | 32 × 1.5 (average depth) | 48 m³ |
| Required flow | 48 ÷ 6 h | 8 m³/h |
| Pump actually chosen | Model delivering 8 m³/h | 9 m³/h |
| Count by area | 32 ÷ 25 = 1.28 round up to 2 | 2 |
| Count by flow | 9 ÷ 9 = 1.00 1 | 1 |
| Count to use | larger of 2 and 1 | 2 |
Why does 1.28 become 2? One skimmer looks after 25 m² of surface, but the pool has 32 m². The first skimmer covers 25 m², leaving 7 m² that nothing covers, so you need a second one. A result of 1.28 means more than one, so it rounds up to 2.
This pool takes 2 EM0020-RC skimmers, and area is what decides it. Each one carries only 9 ÷ 2 = 4.5 m³/h, far below 9 m³/h. Skimmers only (excluding pipework and installation): 2 × 1,444 = THB 2,888.
Use the flow of the pump you actually choose ( 9 m³/h), not the required figure (8 m³/h), because the skimmers carry whatever the pump really draws.
Why area usually decides for home pools
With a 6-hour turnover and 1.5 m average depth, the 25 m² of surface one skimmer covers holds 25 × 1.5 = 37.5 m³ of water, which needs 37.5 ÷ 6 = 6.25 m³/h per skimmer. That is still below the EM0020-RC's 9 m³/h. So for a typical home pool on a 6-hour turnover with an average depth up to about 2 m, the count by area will always be equal to or greater than the count by flow. The flow check starts to matter with a shorter turnover, a very deep pool, or an oversized pump.
Example 2: a hotel pool where flow decides
Say a hotel pool is 10 × 5 m with an average depth of 1.5 m, and because it is heavily used it is designed for a shorter 4-hour turnover.
- Volume: 50 m² × 1.5 = 75 m³ flow 75 ÷ 4 = 18.75 m³/h
- By area: 50 ÷ 25 = 2.00 exactly 2
- By flow: 18.75 ÷ 9 = 2.08 round up to 3
With only 2 skimmers by area, each would carry 18.75 ÷ 2 9.4 m³/h, over the EM0020-RC's 9 m³/h limit. So you need 3 (about 6.25 m³/h each): 3 × 1,444 = THB 4,332.
Hotel pool 10 × 5 m · 1.5 m average depth · 4-hour turnover · always take the larger number
With the HAYWARD SP3400 or EM0180TS-SC, sized at 5 m³/h each, the home pool needs 9 ÷ 5 = 1.8 2 (unchanged), but the hotel pool needs 18.75 ÷ 5 = 3.75 4.
Website prices as of 9 Nov 2026; they may change with promotions and stock. Please check current prices before ordering.
Quick calculator
Leave actual pump flow blank and the calculator works it out from volume ÷ turnover. Once you have chosen a pump, enter that model's flow instead. If the skimmer/main-drain split hasn't been measured, enter 100%. The result is a preliminary count only. Before construction, have a technician check positions, wind direction and pipework.
8 concrete-pool models compared
EMAUXEM0010-RC
EMAUXEM0020-RC
EMAUXEM0030-RC
EMAUXEM0040-RC
EMAUXEM0050-RC
EMAUXEM0180TS-SC
LASWIMPA00249C
HAYWARDSP3400
| Brand / model | Mouth / type | Catalogue flow | Sizing value | Connection | Web price (THB) |
|---|---|---|---|---|---|
| EMAUX EM0010-RC | Standard, compact | 9 m³/h | 9 m³/h | 1½ internal thread | 1,197 |
| EMAUX EM0020-RC | Wide mouth, compact | 9 m³/h | 9 m³/h Reference | 1½ internal thread | 1,444 |
| EMAUX EM0030-RC | Heavy-duty standard | 912 m³/h | 9 m³/h | 1½ or 2 | 2,990 |
| EMAUX EM0040-RC | Heavy-duty wide | 912 m³/h | 9 m³/h | 1½ or 2 | 3,589 |
| EMAUX EM0050-RC | Heavy-duty with extension | 912 m³/h | 9 m³/h | 1½ or 2 | 3,884 |
| EMAUX EM0180TS-SC | 600 mm wide surface opening | 912 m³/h Install manual 5 | 5 m³/h | 1½/2 thread or 1½ solvent | 3,589 |
| LASWIM PA00249C | Standard (ABS) | Awaiting maker data | 5 m³/h (conservative) | Confirm on site | 1,432 |
| HAYWARD SP3400 | Standard, self-adjusting weir + basket | Max 5 m³/h | 5 m³/h | 50 mm slip / 1½ int. / 2 ext. | 2,490 Out of stock |
Prices and stock as of 9 Nov 2026 · Catalogue flow is the figure printed in the manufacturer's brochure, not a recommended design flow. Sizing value is the per-skimmer flow divisor WinWin Pool uses in the formula.
Good to know: the EMAUX brochure lists 912 m³/h for the EM0180TS-SC, but the installation manual for the same model limits it to 5 m³/h and one skimmer per 25 m². We follow the stricter installation manual. For the LASWIM PA00249C we have not yet found a manufacturer-confirmed flow rating, and the actual connection size should be checked before installation.
Choose by application, not price alone
A wide mouth collects floating debris across a wider opening, but it does not necessarily handle more flow. You still need to calculate the count with the formula above.
EM0020-RC
Reference · 9 m³/hWide mouth for outdoor home pools with a moderate leaf load.
View productEM0030-RC / EM0040-RC
Heavy-duty range for demanding sites or heavy debris. Choose standard (0030) or wide (0040) by debris load.
EM0030 EM0040EM0050-RC
For walls that need an extension piece. Measure the actual wall thickness before ordering.
View productEM0180TS-SC
600 mm surface opening for a particular waterline look. It does not raise the flow per skimmer (keep to 5 m³/h).
View productPA00249C
Standard ABS mouth for customers who want the LASWIM brand. Confirm flow and connection size with our team first.
View productSP3400
Standard ABS mouth with a self-adjusting weir and debris basket. Manufacturer-recommended maximum 5 m³/h per skimmer · check stock before ordering.
View productA simple decision path
- Check the pool type. The models in this article are for concrete pools.
- Wall needs an extension EM0050-RC · want a 600 mm opening EM0180TS-SC
- Heavy debris or a demanding site EM0030-RC (standard) or EM0040-RC (wide)
- Outdoor home pool with moderate leaves EM0020-RC · general use EM0010-RC
- LASWIM or HAYWARD specified standard mouth only (PA00249C / SP3400)
- Calculate the count by area and by flow, and use the larger number
- Have a technician check positions, wind, return inlets and pipework before construction
Placement matters as much as quantity
Put skimmers on the downwind side so the wind pushes debris towards them, and place return inlets on the opposite side so the surface current flows into the skimmers. Long pools, L-shaped pools or pools with dead corners may need extra skimmers even when the formula says you have enough. Keep the water level at about the middle of the skimmer opening so the weir works properly.
FAQ
How many skimmers does an 8 × 4 m pool need?
At 1.5 m average depth the pool holds 48 m³; a 6-hour turnover needs about 8 m³/h (so a pump of roughly 9 m³/h). By area, 32 ÷ 25 = 1.28, rounded up to 2; by flow, 9 ÷ 9 = 1. So use 2 EM0020-RC skimmers. With the HAYWARD SP3400 or EM0180TS-SC (5 m³/h each) it is also 2.
Does a wide-mouth skimmer handle more flow?
Not necessarily. A wide mouth collects surface debris across a wider opening, but design flow per skimmer depends on the manufacturer's specification and the pipework.
Which pump flow should I use?
The actual operating flow from the pump curve at your system's head (including losses from pipes, filter and fittings), not the maximum flow on the box, which is usually much higher than real-world flow.
Does a main drain change the calculation?
If you have measured what share goes to the main drain, you can deduct it. If not, assume 100% goes through the skimmers, because the main-drain valve may be closed at any time in normal use.
Can you have too many skimmers?
If the pump is small for the number of skimmers, suction at each one becomes too weak to work the weir and debris is not drawn in. Keep the skimmer count balanced with the pump size.
Let the WinWin Pool team help you choose
Before ordering, send our technical team the details below. It helps avoid equipment that doesn't suit your system and costly fixes on site.
- Pool drawings and water surface area
- Pump model and operating flow
- Photos of the pool wall and return inlet positions
References
