Is your pool warm enough to enjoy, or does it sit unused because the water never quite gets there? An electric tankless water heater built for pools, like the EcoSmart Smart Pool 27, takes a different approach from a storage tank. It heats water as it flows through the unit, only when the pool system calls for heat, instead of keeping a large tank hot around the clock. If that sounds appealing, this guide will help you understand how it works and what to plan before you buy.
This page is a practical guide to the product type named in the listing: an EcoSmart Smart Pool 27 electric tankless water heater for indoor installation, with a stated flow rate of 25 GPM. It explains on-demand heating, what flow rate means for a pool, how installation is usually planned, and what to ask a contractor. It is not a list of factory specifications, so use it to shape your questions rather than as a substitute for the manual.
What an electric tankless pool heater is
A tankless water heater has no storage tank. Cold water enters one side, passes over electric heating elements inside the unit, and leaves hot on the other side. The heater only draws power while water is flowing and heat is needed, and it stops when the flow stops. For a pool, the heater sits in the circulation loop: the pool pump pushes water through the heater, the heater raises its temperature, and the warmed water returns to the pool.
The Smart Pool 27 name points to a unit sized for pool duty rather than a single tap. Pool heaters deal with far larger volumes of water than a household shower heater, and they run for longer stretches, so the design, the electrical supply, and the plumbing all need to match the job. The listing describes this model as electric, tankless, and for indoor installation, which already tells you a lot about the kind of setup it expects.
How on-demand heating works for a pool
Pool heating is a slow, steady job. A pool holds a large body of water, and warming it means adding heat over many hours, not minutes. A tankless heater in the pool loop adds a fixed amount of heat to the water passing through it on each circuit. The pool pump keeps the water moving, the heater keeps adding heat, and the pool temperature climbs gradually until it reaches the set point.
The thermostat and the flow switch are the two controls that matter most in daily use. The thermostat sets the target water temperature, and the heater fires only when water is flowing and the temperature sits below that target. A flow switch protects the heating elements by making sure they never run dry. If the pump stops, the heater stops too. That simple link between flow and heat is what makes a tankless design safe to leave in the loop.
What the 25 GPM flow rate means
GPM stands for gallons per minute, and it describes how much water can pass through the heater. The listing states a flow rate of 25 GPM for this model. In plain terms, that is the volume of water the unit is built to handle as it flows through. Flow rate matters because a pool heater only works when water moves through it at a rate the design expects.
Too little flow can trip safety controls or leave the heater cycling on and off, while too much flow can push water through faster than the heater can warm it on each pass. Your pool pump, your pipe size, and the rest of the circulation loop all shape the real flow rate in your system. Ask your contractor to check the pump and plumbing against the heater's stated flow rate, and to confirm that the loop can deliver steady flow in the range the heater is designed for.
Indoor installation: what to plan
The listing describes this heater as an indoor unit, so plan for a sheltered spot with protection from weather and freezing temperatures. A garage, a pool equipment room, or a covered utility space is the usual kind of location. The unit needs clear space around it for air, for service access, and for a technician to reach the controls and connections without dismantling half the room.
Electric tankless pool heaters draw a large amount of power when they run, so the electrical supply is often the biggest part of the job. A licensed electrician should check the service panel, the available capacity, and the wiring and breaker sizes the heater requires. Do not guess at this. The manual and local electrical rules decide what is needed, and the panel may need an upgrade before the heater can run. Sorting the electrical work out before the heater arrives avoids an installed unit that cannot be switched on.
Plumbing the heater into the pool loop
Plumbing is the other half of the installation. The heater connects into the circulation loop, usually after the filter and before any chemical feeders or salt system, so that clean filtered water passes through it and treated water does not sit in the heating chamber. Shut-off valves on both sides let you isolate the heater for service without draining the pool, and a bypass line lets the pump run while the heater is out of service.
Pipe size, fittings, and the layout of the loop all affect flow, so the installer should plan the run with short, straight pipework where possible and avoid sharp bends that choke the flow. A drain point near the heater makes winterising and service far easier. If the pool will sit unused in cold weather, ask how the heater and its pipes should be drained so trapped water cannot freeze and crack a fitting.
Sizing the heater for your pool
Sizing a pool heater is not a matter of picking the largest unit on the shelf. The right size depends on the pool volume, how warm you want the water, how quickly you want it to warm up, and how much heat the pool loses to wind, night air, and evaporation. A pool cover makes a large difference here, because a covered pool loses far less heat overnight than an open one.
A good contractor will ask about your pool size, your target temperature, and how you use the pool before recommending anything. Bring those answers to the conversation: the pool dimensions, whether you swim daily or only at weekends, whether you heat year-round or only in a short season, and whether you use a cover. Those details matter more than any single number on a listing, and they are what turn a guess into a sensible plan.
Running costs and daily use
An electric tankless heater uses electricity only while it heats, so running costs track closely with how often the pool needs heat and how much heat it loses between swims. A pool that is heated all season with no cover will cost far more to run than the same pool heated for weekend use under a cover. Wind exposure, night temperatures, and the target water temperature all push the cost up or down.
To keep costs in check, use a pool cover whenever the pool is not in use, set the thermostat to the lowest temperature you genuinely enjoy, and heat the pool for the hours you swim rather than holding it at full temperature all week. A timer on the pump and a routine of covering the pool at night are the two cheapest habits in pool ownership, and they do more for your running costs than any single piece of equipment.
Care and maintenance
Tankless pool heaters need little daily attention, but they do need regular checks. Keep the filter clean, because a dirty filter chokes flow and the heater depends on steady flow. Watch the water chemistry, since unbalanced water can scale the heating elements and shorten their life. Check for drips around the unions and fittings now and then, and listen for any change in the sound of the pump or the heater.
Once a year, have a technician look over the unit: the electrical connections, the flow switch, the thermostat, and the condition of the elements. In hard-water areas, ask whether descaling or a water treatment plan is worth doing. At the end of the season, follow the manual for draining and winterising if the pool will sit cold. A little attention each season keeps a tankless heater reliable for years.
Questions to ask your contractor
Before you commit, ask your contractor to walk the job with you. Ask whether your electrical panel can carry the heater and what upgrade, if any, would be needed. Ask where the heater will sit, how the plumbing loop will run, and where the shut-off valves and drain points will go. Ask how the heater will be sized for your pool and what warm-up time you can expect in your climate.
Also ask about the warranty and the service plan. Find out what the warranty covers, who carries out warranty work in your area, and how often the unit should be serviced. Ask what happens if the flow rate from your pump does not match the heater, and what the fix would be. A contractor who answers these questions plainly, in writing, is the one you want doing the work.