How big a water pump do you need for your shower?

1. The number of shower heads you have: Each shower head typically requires a flow rate of around 2.5 gallons per minute (GPM). So, if you have two shower heads, you'll need a pump that can provide at least 5 GPM.

2. The height of your shower head: The higher your shower head is, the more pressure you'll need to get the water to flow properly. For every 10 feet of height, you'll need to add about 1 psi (pound per square inch) of pressure.

3. The length of your shower pipe: The longer your shower pipe is, the more friction there will be, which can reduce the water pressure. For every 100 feet of pipe, you'll need to add about 5 psi of pressure.

4. The type of shower head you have: Some shower heads are more efficient than others and require less water pressure to operate properly. Check the manufacturer's specifications for your shower head to see what the recommended pressure is.

Once you've determined the factors above, you can use the following formula to calculate the minimum required flow rate for your shower pump:

```

Flow rate (GPM) = (# of shower heads) * (GPM per shower head) + Height (ft) / 10 * Pressure (psi) + Length (ft) / 100 * Pressure (psi)

```

For example, if you have two shower heads, each with a flow rate of 2.5 GPM, and your shower head is 8 feet high and your shower pipe is 50 feet long, you would need a pump with a minimum flow rate of:

```

Flow rate (GPM) = (2 shower heads) * (2.5 GPM per shower head) + (8 ft / 10) * 1 psi + (50 ft / 100) * 5 psi

Flow rate (GPM) = 5 + 0.8 + 2.5

Flow rate (GPM) = 8.3 GPM

```

Therefore, you would need a water pump with a flow rate of at least 8.3 GPM to ensure adequate water pressure for your shower.