Residential Tank Sizing Calculator

Step 1: Select your preferred unit of measure

Step 2: Calculate Drawdown

Pump delivery rate (per minute)
GPMLPM
Desired minimum pump running time in minutes
(1 minute, 45 seconds = 1.75 minutes)
Minutes
Calculate Drawdown

Please enter a number in both 'pump delivery rate' and 'desired minimum pump running time' fields.

We could not calculate your minimum drawdown based on the information you provided. Please make changes to the information as necessary, or supply your own calculated volume below.

We calculated the minimum drawdown (available water volume) required for you, but you can adjust it as necessary.*
GallonsLiters
*
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.

Step 3: Calculate Drawdown Factor

Minimum system pressure (cut-in)
PSIG / kPa / bar
Maximum system pressure (cut-out)
PSIG / kPa / bar
Calculate Drawdown

Please select your minimum system pressure (both cut-in and cut-out).

We could not calculate your drawdown factor based on the information you provided. Please make changes to the information as necessary, or supply your own estimated drawdown factor below. You may consult our drawdown chart for reference.

We tried to calculate the drawdown factor for you, but you can enter your own if necessary.*
*
In keeping with current industry standards, drawdown factors are based on Boyle’s law. Actual drawdowns will vary depending upon system variables including the accuracy and operation of the pressure switch and gauge, actual precharge pressure, and operating temperature of the system.

Step 4: Calculate Tank Size

I need a Low-Profile Tank (for small spaces like a crawl space or under a mobile home)
There were errors with your form. Please make sure all fields have been filled out correctly.

Based on your entries, we calculated the following:

Recommended Model:
Minimum Capacity: GallonsLiters

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.

View the Drawdown Chart
Download the Drawdown Chart (687 Kb)

See the complete model and specification list below for other tank options.

Specifications

WM Series 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	125 / 862 / 8.6	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	125 / 862 / 8.6	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	125 / 862 / 8.6	8.9 / 33.5	16 / 41	44 / 112	1 3/4 / 4.4	1" male NPT	24.75 /11.2	9
WM-11 / WM0130 QC	35 / 132	125 / 862 / 8.6	10.6 / 40.1	21 / 53	33 / 83.8	2 1/4 / 5.7	1 1/4" male NPT	32 / 14.5	4
WM-12 / WM0150	40.3 / 153	125 / 862 / 8.6	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	125 / 862 / 8.6	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	125 / 862 / 8.6	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	125 / 862 / 8.6	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 vary depending upon system variables, including the accuracy and operation of the pressure switch and gauge and operating temperature of the system.