WellMate Pentair Water Technical

Residential Tank Sizing Calculator | Tank Replacement Guides

Basic sizing and selection requirements

There are three factors to consider when selecting the proper size WellMate for your Water system:

The pump delivery rate in gallons/liters per minute (GPM/LPM)
The recommended minimum running time of the pump
The minimum (cut-in) and maximum (cut-out) system pressure parameters

Once these factors are known, the following calculations will determine, in most cases, the correct model to meet your specifications.*

Step 1: Calculate Drawdown

Pump delivery rate in GPM/LPM
GPM/LPM
Desired minimum pump running time in minutes
(1 minute, 45 seconds = 1.75 minutes)
Minutes
Click "Calculate Drawdown". This is the minimum drawdown or available water volume required in Gallons/Liters.*

Gallons/Liters.

Step 2: Calculate Tank Size

Minimum system pressure (cut-in)
PSIG/kPa/bar
Maximum system pressure (cut-out)
PSIG/kPa/bar
Using table #2 (click here), find the drawdown factor applicable to lines #4 and #5.
Factor
I need a Low-Profile Tank (for small spaces like a crawl space or under a mobile home)
Select to calculate in gallons or liters

This is the WellMate model we recommend based on your entries.

Model Number:

* If a volume of water needed is greater than the amount calculated on line #3, enter that amount on line #3 in place of the calculated volume.

See complete Model & Spec list below for other tank options.

WM Performance Data

Model Number	Capacity gal / liter	Maximum Operating Pressure psi / kPa / Bar	Drawdown 30/50 Setting gal** / liter	Diameter* inch / cm	Overall Height* inch / cm	Height* inlet/ outlet to floor inch / cm	System Connection	Assembly Weight* lb / kg	Pallet QTY.
WM-4 / WM0060	14.5 / 55	100 / 700 / 7.0	4.4 / 16.5	16 / 41	26 / 66	1 3/4 / 4.4	1" male NPT	14.5 / 6.6	9
WM-6 / WM0075	19.8 / 75	100 / 700 / 7.0	5.9 / 22.5	16 / 41	32 / 81	1 3/4 / 4.4	1" male NPT	17.75 / 8.1	9
WM-9 / WM0120	29.5 / 112	100 / 700 / 7.0	8.9 / 33.5	16 / 41	44 / 112	1 3/4 / 4.4	1" male NPT	24.75 /11.2	9
WM-12 / WM0150	40.3 / 153	100 / 700 / 7.0	12.1 / 45.8	16 / 41	57 / 145	1 3/4 / 4.4	1" male NPT	30 /13.6	9
WM-23 / WM0300	79.6 / 301	100 / 700 / 7.0	23.8 / 90.4	21 / 53	62 / 157	2 1/4 / 5.7	1 1/4" male NPT	65.7 / 29.8	4
WM-14WB / WM0180	47.1 / 178	125 / 862 / 8.6	14.1 / 53.5	21 / 53	41 1/4 / 105	2 1/4 / 5.7	1 1/4" male NPT	43 / 19.5	4
WM-20WB / WM0235	60.0 / 227	125 / 862 / 8.6	18.0 / 68.1	24 / 61	41 1/2 / 105	2 1/4 / 5.7	1 1/4" male NPT	50 /22.7	4
WM-25WB / WM0330	86.7 / 328	125 / 862 / 8.6	26.0 / 98.5	24 / 61	55 1/4 / 140	2 1/4 / 5.7	1 1/4" male NPT	72.75 / 33.0	4
WM-35WB / WM0450	119.7 / 453	125 / 862 / 8.6	35.9 / 135.9	24 / 61	74 1/4 / 189	2 1/4 / 5.7	1 1/4" male NPT	95 / 43.1	N/A

Low-Profile Performance Data

Model Number	Capacity gal / liter	Maximum Operating Pressure psi / kPa / Bar	Drawdown 30/50 Setting gal** / liter	Diameter* inch / cm	Overall Height* inch / cm	Height* inlet/ outlet to floor inch / cm	System Connection	Assembly Weight* lb / kg	Pallet QTY.
WM-6LP / WM-LP-075	19.3 / 73	100 / 700 / 7.0	5.8 / 21.9	24 / 61	20 1/4 / 51	2 1/4 /5.7	1" male NPT	22.75 / 10.3	8
WM-10LP / WM-LP-130	34.5 / 131	100 / 700 / 7.0	10.4 / 39.2	24 / 61	28 /71	2 1/4 /5.7	1" male NPT	29.5 / 13.4	8

Note: Maximum external operating temperature 120°F (49°C). Maximum internal operating temperature 100°F (38°C). Minimum operating temperature 40°F (4°C).

* Diameter, height and weight may vary slightly without notice.

** In keeping with current industry standards, drawdown factors are based on Boyle's law. Actual drawdowns will very depending upon system variables, including the accuracy and operation of the pressure switch and gauge and operating temperature of the system.