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Water, Water, Everywhere, and All Those Drops to Heat


You may not be surprised to hear that Float Centers have a hefty water requirement. You may, however, be surprised to hear that the majority of the water demand you’ll be facing on a day-to-day basis is going to be in the form of showers and (if you’re doing any laundry on-site) a washing machine.

This water demand is going to be mostly hot water (not too many people like cold showers, and hot water works best on those salty towels). Because of this, properly choosing your water heater to meet the demand is key.

This guide will serve as an introduction to the different water heater options available, and how to size them for the requirements of your float center. We’ll also get into how factors such as energy usage and cost-over-time should be taken into consideration when deciding upon your water heater.

Types of Water Heating Systems

The two most common types of water heating systems are storage tank models powered by either gas or electricity, though there are other options available, some of which are mentioned below.

gas water heaters for float tank centersGas storage tank water heaters use a small gas flame to heat the water, resulting in the ability to heat water very quickly. Generally, gas water heaters will be more expensive than their electric counterparts. The gas flame, and the generally lower costs of gas, mean it’s less expensive in the long run to operate a gas vs. an electric heater.

On a side note, storage tank water heaters suffer from standby heat loss (even though a water heater in a float center doesn’t do much standing by). One way to cut down on heat loss is to purchase a well insulated unit.

electric water heaters for float tank centersElectric storage tank water heaters use an electric heating element to heat the water, and are usually less expensive than gas water heaters to purchase. Since they use electricity, they are more efficient than their gassy friends. However, they end up costing more over time in energy usage.

Since they use an electric heating element, they cannot heat the water as quickly as gas water heaters, which can be a problem in a high-usage environment like a float center.

on demand water heaters for float tank centersOn-demand water heaters (or tankless water heaters) heat water immediately prior to being used. Similar to storage tank water heaters, these are available in both gas and electric models. Tankless water heaters are also gaining prominence, as they use less energy over time since they do not suffer from standby heat loss.

If you decide to install tankless water heaters in your float center, make sure your plumber understands the load you’ll be placing on them. A high end gas fed unit is only capable of supplying around 4-6 gallons per minute (2-3 showers running simultaneously) of hot water. [Note: in plumbing terms, “hot water” is water that has been heated 70°F from the temp of the source water – usually around 50°F.]

So, depending on the size of your float center and your local water supply, you may need several units to handle the hot water demand required from all those salty floaters showering. Tankless water heaters can be relatively expensive to install, though they can definitely yield a good investment on future energy savings.

solar water heaters for float tank centersSolar Heating is a great option if you happen to find yourself in one of those places where the sun shines enough (which is, surprisingly, most places). Solar water heating systems can carry a hefty price tag, but just like the on-demand heaters mentioned above, they are an investment for future savings.

Furthermore, you’ll use a lot less energy, have a much greener float center, and definitely save on your energy bills as well.

Sizing Your Water Heater

Properly sizing your water heater(s) directly depends on your desired output. Tankless water heaters are rated by the maximum potential water temperature rise at a given flow rate. Storage tank water heaters are rated by the amount of heated water a unit can supply per hour (also known as the First Hour Rating).

First Hour Rating

One common method of describing performance capacity of a water heater is the First Hour Rating (aka First Hour Delivery). This is the calculated amount of how much hot water a fully heated water heater can deliver in the first hour period.

This is a measure of how many gallons of hot water your water heating system can provide, from its fully heated state. Pay close attention to the first hour rating of your water heater, as the bulk of your water will be used in spurts during transition times, and there will likely be reasonable time in between to reheat water.

Recovery Rate

Another very important metric to pay attention to in choosing your water heating system is the recovery rate. This is essentially the amount of hot water that the system is able to create, and is given over time, usually in gallons per hour (GPH).

This is often noted on the specifications of the water heating system, and you can use it to determine how quickly your system can heat water up over time, allowing you to figure out your initial heating time from an empty tank as well as the water amount heated in various period of down time. Gas models outperform electric models in this category.

A Grain of Salt: Since a float center is using it’s water heater pretty consistently throughout the day, choosing a high efficiency model with a fast recovery rate is probably going to be your best best. Also, since so much energy is used to keep water warm while in storage, choosing a well insulated model is a pretty good idea as well

Hot Water Requirements for Showers

water heaters for showersThe two showers that every customer takes are very important in a float center; the first removes oils from customers’ bodies before they enter the tank, and the second allows the customer to rinse the Epsom salt water off afterwards.

Federal regulations limit shower heads to 2.5 gallons per minute (GPM) at 80psi or 2.2 gallons per minute at 60psi. There are low-flow shower heads available which can lower this to even half of this, and some sort of low-flow shower head is definitely recommended for a float center.

Let’s assume a shower head with a 2GPM rating, and an average length of shower of five minutes. This means that 10 gallons of water are used on average for each shower taken.

A Grain of Salt: While your customer’s shower length will be limited (most centers run floats back to back, and our customers are often prompted of their time constraints during a walkthrough), there is still a fairly wide range of shower lengths customers might take. Showers are one of the largest contributors to your water bill, and I wrote another post (Don’t Squander Water in your Showers) covering some tips on lowering the amount of time people spend showering. Even knocking one minute off of all or your customer’s showers can have a drastic effect on your water bill over time.

Laundry and Utility Sink

An average load of laundry washed in a high efficiency machine will use about 7 gallons of hot water (more if you use a heavy duty cycle for all those salty float towels). If you’re doing a load (or loads of laundry) in the down-time between transitions, you may be sapping hot water from upcoming showers.

If you plan on cleaning anything, you’re likely going to be sapping from your hot water as well: a few gallons to fill a mop bucket, washing dishes and neck pillows, cleaning the bathroom, etc.


Let’s take a look at the range of hot water needs of a center. We’ll assume float centers run back-to-back floats (one customer finishes their float and their post-float shower, while another customer gears up to shortly thereafter take their pre-float shower).

This means that in the “first hour” period of a storage tank model discussed above, you’ll need a decent amount of hot water. 20-40 gallons for a single float tank. For a 4 tank center, anywhere from 80-110 gallons, and for a 6 tank center, 100-130 gallons.

If you install tankless water heaters, remember that they are rated in gallons per minute of flow at a desired target temperature rise. You’re considering instant demand.  You may only be able to supply two showers per water heater. You might also consider plumbing multiple units in series to increase efficiency.

Grain of Salt: Larger units capable of producing the desired high output can climb in price very quickly. This is why some centers have opted to run a dual setup consisting of two smaller units to get the first hour rating they desire.

It’s important to note these are fairly conservative estimates. The above are just estimates, you’ll want to do the math with your specific center’s water usage, and you’ll likely want to overshoot whatever estimates you arrive at to ensure that you have plenty of wiggle room and aren’t stressed about water usage.

Maybe you’ll need much more than a couple of buckets to mop your center, or you have people may take longer showers than 5 minutes–we all know how fast time passes in a warm shower, especially when you’re nice and floaty.

Definitely check out the tips in the Don’t Squander Water post I mentioned before if you’re concerned about cutting down shower time. As always, if there are any questions about what I discussed here, or anything else on the road to opening your float center, definitely feel free to reach out to me at frank@floathq.com.