Written October 2026 from our own condo jobs and price book, with ClimateMaster, Daikin Applied, Trane, the Department of Energy, the EPA and the Code of Virginia read at the source the same week.
A water source heat pump is a heat pump with no outdoor unit. It stands in a closet or hangs above the ceiling of your condo and trades heat with the building’s water loop, pipes that a cooling tower and a boiler keep at a steady temperature, instead of with outside air. They’re common in Northern Virginia’s high-rise and mid-rise condos, from the Rosslyn-Ballston corridor to Crystal City, Alexandria, Reston and Tysons. What replacing one costs with us. From about $152 a month at 0% APR for 60 months, the whole price financed, on approved credit. The installed price is $9,100 to $10,300, in the same closet or ceiling space. If yours has stopped heating or cooling, check the filter and switch its breaker off and on once before you call, because that’s how its safety lockout resets. If it locks out again, or there’s water on the floor, call (703) 997-9757. Condo jobs book on our condo HVAC page.
The system we put in first
Built to take a beating. Put in by our crew.
Heat lamps, snow and rain on one outdoor unit: that’s Trane’s own film. We’re a Trane Comfort Specialist, on Trane’s own dealer locator, and when you pick a Trane, our crew puts it in.
Films: Trane’s own.
Water source heat pump: the water loop is the outdoor unit
Every heat pump moves heat. The one beside a house moves it between your rooms and the outside air. A water source heat pump does the same job with water: in cooling it pulls heat out of your rooms and puts it into the water flowing through the unit, and in heating it runs in reverse and pulls heat out of that water. The compressor, both coils and the fan all live in the one cabinet in your closet, so the refrigerant never leaves it.
The water is a loop the whole building shares. Supply and return pipes called risers run up through the walls to every unit, and the building’s pumps keep the water moving. ClimateMaster’s installation manual says these cooling tower and boiler systems typically hold the loop between 60 and 90 degrees: the tower sheds the heat the units put in all summer, and the boiler adds heat in winter. On a spring afternoon a sunny unit that’s cooling and a shady one that’s heating trade heat through the same water, “recovering otherwise wasted energy in some spaces,” as ClimateMaster puts it. Your unit runs on its own schedule whatever your neighbors are doing, and “if one unit goes down, the other units are not affected.”
Because the water stays in that band, the unit is rated differently from a house’s heat pump: EER and COP at fixed water temperatures under ISO 13256-1 (86 degrees for the cooling rating and 68 for heating on a water loop), not SEER2 and HSPF2, so don’t hold its numbers up against an outdoor unit’s. ClimateMaster’s 2-ton vertical stack chassis is rated at an EER of 16.1 and a COP of 5.0 on a water loop; the Department of Energy’s floor for that size is 13.0 and 4.3.
Is the box in your closet a water source heat pump?
Four things give it away, and you can check them all with the closet door open and the unit’s panels left on.
- No outdoor unit. No condenser on a balcony, a roof pad or a wall louver belongs to your condo. The loop does that job.
- Two water connections. Low on the cabinet, or above a ceiling unit, two stainless steel braided hoses run from the unit to pipes coming out of the wall, each with a valve handle: the supply and return from the risers. Manufacturers sell this as a hose kit, sometimes with a Y-shaped strainer built in.
- A compressor in the closet. When it starts, you hear the hum right there behind the door, not out a window.
- The data plate. The names we see are ClimateMaster, Daikin, McQuay, Trane, Comfort-Aire, Bosch and California Heat Pump, usually with “water source” or “WSHP” on the label. The size hides in the model number: a 24 or 024 means 24,000 Btu an hour, which is 2 tons. Take a phone photo of the plate; it’s the first thing we’ll ask for.
Three look-alikes get called water source heat pumps and aren’t. A First Co or Aquatherm air handler piped to your own water heater heats with hot water from that tank (First Co says the water heater “becomes a dual function appliance”), with a separate air conditioner outside or through the wall: see our First Co and hydro-air guide. A MagicPak is one self-contained unit set into an outside wall behind a louver. And a fan coil on the building’s chilled and hot water has no compressor in your closet at all; if your building switches the whole system between a heating season and a cooling season, that’s usually what you have. A heat pump outside a townhouse or house is an air-source unit, and heat pump replacement is its page.
Your part and the building’s part
Your condominium’s declaration decides who owns what, and the answer changes from building to building. Where the declaration is silent, Virginia law fills the gap. Section 55.1-1912 of the Code of Virginia says that when pipes, ducts, wires or other apparatus run partly inside and partly outside your unit, “any portions serving only that unit are a part of that unit,” and the portions serving more than one unit are common elements. Section 55.1-1955 then puts the upkeep with the ownership: unless the documents say otherwise, you maintain, repair and replace your unit and pay for it, the association does the same for the common elements, and a problem that starts in the common elements is the association’s. For a water source heat pump, that default usually splits like this:
| Part | Under Virginia’s default | Who to call |
|---|---|---|
| Cooling tower, boiler, loop pumps, water treatment | The association’s: they serve every unit | Management or the building engineer |
| Supply and return risers in the walls | The association’s | Management |
| The shared condensate drain riser | The association’s | Management |
| The valves and hoses between the riser and your unit | Usually yours: they serve only your unit | Us, once the building confirms the loop is fine |
| The heat pump, its thermostat, its drain line and trap | Yours | Us |
| The filter | Yours | You, every month |
Read your declaration and any maintenance chart the association publishes before you call anyone, because plenty of buildings move the line, most often at the valves. The working rule is simpler. If several units on your stack lost heat or cooling at once, it’s the loop, and the building engineer is your first call. If it’s only yours, it’s the box, and that’s us. Either way, only the building can shut down a riser, so any work that opens the water side gets scheduled with management. More on how the Arlington corridor buildings differ is in heating repair in Arlington.
When it acts up: what you notice and what it usually means
A water source heat pump protects itself. When the water stops flowing, the loop drifts out of range or the drain backs up, its control shuts the compressor off and holds it off, and the fan often keeps running. That’s why the most common complaint is air coming out at room temperature. ClimateMaster’s troubleshooting chart is a good map of what trips what:
| What you notice | What it usually is | What to do |
|---|---|---|
| Fan blows, air is neither warm nor cool | A safety lockout. In cooling: low water flow (a clogged strainer, a closed valve) or loop water too warm. In heating: low water flow or loop water too cold | Breaker off and on once. If it locks out again, call, and ask the building about the loop |
| Water in the pan or on the floor, and the unit shut itself off | A blocked drain or trap, and the overflow switch did its job | Thermostat to Off, towels down, call |
| A hum you hear through the walls when it runs | Hoses or pipes touching the structure, carrying compressor vibration into the building | Book a visit |
| Runs in short bursts | A clogged filter, or a unit too big for the space | Change the filter; book a visit if it keeps doing it |
| A damp hose or a drip at a fitting | An aging hose or a loose connection | Close the two valves if they turn easily, then call |
| Nothing at all, thermostat blank | Power or the thermostat | Batteries, then the breaker, then call |
Sound is its own complaint. The compressor lives in your closet, sometimes a few feet from a bed. Daikin offers a compressor sound blanket on its 2- to 3-ton vertical stack units, and ClimateMaster sells an UltraQuiet package. ClimateMaster’s manual adds two install rules: set the unit’s return opening at 90 degrees to the closet’s return grille, and keep the hoses off the walls and framing, because “compressor vibration may be transmitted through the hoses to the structure, causing unnecessary noise complaints.” When we replace a unit in a closet next to a bedroom, the sound blanket goes in.
Before you call: four checks and one question for the building
- The filter. Behind the return grille, in the closet’s louvered door or in a rack on the unit. ClimateMaster says to look at it every month and never to run the unit without one. A filter you can’t see light through starves the coil, and that alone can trip a lockout.
- The thermostat. Heat or Cool, set a few degrees past the room, fresh batteries if the screen is blank.
- One reset. Switch the heat pump’s breaker off, wait a minute, and switch it back on; resetting the power is ClimateMaster’s answer to a locked-out unit. If it locks out again, something is stopping the water or the air, and another reset won’t find it.
- Water. Water in the pan or on the floor means thermostat to Off, towels down, and a call. Don’t tape down or bypass the overflow switch.
Then ask the building one question: is the loop running normally, and has anyone worked on the risers? The engineer knows whether the boiler is on for the season, whether the cooling tower is still running, whether a riser was drained for a repair, and whether the valves at your unit were closed for that work and never reopened. Riser work also lets air into the water; in ClimateMaster’s words, “any unit plumbing maintenance work can introduce air into the piping system.” If neighbors on your stack have the same problem, that’s your answer.
Water source heat pump replacement in a high-rise: what the day takes
Most of the work happens before the old unit comes out.
The same footprint, measured. The new unit has to match the old one: vertical (standing in a closet) or horizontal (hung above a ceiling), which side the return air comes in, where the supply duct leaves, and where the water and drain connections sit. We measure the cabinet, the closet door and any ceiling access panel, because a unit that’s right on paper and won’t fit through the opening costs a second day.
Vertical stack units are their own case. In many high-rises the unit is a tall, narrow cabinet with the risers built in, stacked floor over floor, and the usual job is a new chassis (the compressor, coils and fan) slid into the cabinet that’s already there. ClimateMaster builds its Tranquility SH chassis to fit “without having to tear out existing cabinets or modifying riser stacks,” so no drywall gets opened. A 2-ton SH chassis is about 21½ inches deep, 22½ wide and 41½ tall, and rides any elevator. A whole new cabinet is bigger: Daikin’s 2- to 3-ton vertical stack cabinet is 24 inches square, built to split in two so it can be carried to upper floors.
The water side. The valves at your unit get closed, the old hoses come off, and the unit drains. In older buildings those valves often haven’t been turned in years, and if one won’t close all the way, management has to shut and drain the riser on its own schedule. New braided hoses go on with the new unit. ClimateMaster calls for a 20 to 30 mesh strainer ahead of its units, and lists a plugged strainer among the causes of lockouts in heating.
The drain. ClimateMaster’s manual says every unit must have “its own individual trap” before it ties into the condensate riser, and a way to flush the line. A shared drain that runs slow drains badly for every unit on it, so we check how yours flows before the new unit goes in.
The day. Ask management what it needs first: an elevator reservation, the hours work is allowed, any contractor paperwork. Our condo quotes are written as one day on site for two or three of our technicians: the old unit out and hauled away, the new one set, hoses, a new electrical disconnect, the drain and its overflow switch, the thermostat, and a start-up test. If the water heater shares the closet, ask about doing both on one visit.
The R-454B question. New water source heat pumps don’t use R-410A anymore. The EPA capped refrigerants for this class of equipment at a global warming potential of 700, starting with units built in 2025 (40 CFR 84.54; the 2023 rule names water source heat pumps in that class). ClimateMaster’s replacement chassis and Trane’s Axiom line use R-454B, and Daikin’s newer units use R-32. On a water source heat pump the change stays inside the cabinet, since the refrigerant never leaves it: no line set to replace, no outdoor unit to match. And it isn’t a reason to replace a unit that works. The same rule “does not restrict the use of HFCs in ordinary repair and servicing,” so an R-410A unit can still be repaired.
Water source heat pump replacement cost in Northern Virginia
From about $152 a month at 0% APR for 60 months, the whole price financed, on approved credit. The installed price is $9,100 to $10,300, for a new water source heat pump on the building’s loop in the same closet or ceiling space, with the isolation valves and hoses checked and a sound blanket where the closet is next to a bedroom. That span comes from the units we’ve replaced and quoted in Arlington condo buildings between Courthouse and Ballston and in Fairfax: a 2-ton Daikin with a sound blanket in place of an old McQuay, 2-ton Comfort-Aire units with new hoses and a sound blanket, and others like them. The price is in writing before any work starts. Our financing page has the plans, and whatever deals we’re running are on our offers page.
Repair or replace? What we’d do in your shoes: if the unit is under about 15 years old and the trouble is a valve, a hose, the fan motor, a control board or a clogged strainer, repair it. If it’s past 20 and the compressor or the water coil has gone, replace it, and put in the sound blanket and new hoses while the closet is open. A new compressor in a 20-year-old cabinet is a new part on old coils, an old fan and old controls, and the next failure is already in there with it.
How long a water source heat pump lasts
ClimateMaster cites ASHRAE for a life expectancy of more than 20 years on water source heat pump systems, and part of the reason is easy to see: the unit works against water held between 60 and 90 degrees instead of August heat and January cold. What shortens it is mostly the water and the hoses. ClimateMaster’s manual says corrosive water cuts service life, tells installers to keep checking the hose assemblies, and traces dirty loops to old iron or galvanized piping corroding inside the system. Your share of the upkeep comes from the same manual: the filter looked at every month, the drain inspected twice a year, and a yearly check of the air coil and the compressor’s electrical draw.
Water source heat pump vs geothermal
Same machine, different water. A geothermal heat pump is a water source heat pump whose loop runs through pipes in the ground or a well instead of a cooling tower and a boiler; AAON, which builds both, notes that a bore field can take the place of the boiler and tower. ClimateMaster sells the same Tranquility models for both and rates them both ways under ISO 13256-1: a water loop at 86 degrees for cooling and 68 for heating, a ground loop at 77 and 32. That shows the trade: the same 2-ton chassis puts out 28,200 Btu an hour of heat from 68-degree loop water and 18,400 from 32-degree ground water. For a condo owner it’s academic. Your unit runs on the loop the building has, changing that is the association’s decision, and what you choose is the box.
Water source heat pump questions, answered
What is a WSHP?
Short for water source heat pump: a heat pump in a closet or ceiling that heats and cools by trading heat with a building’s water loop instead of outside air. In Northern Virginia they’re common in high-rise and mid-rise condos.
How does a water source heat pump work?
In cooling, its compressor pulls heat out of your rooms and puts it into the water flowing through the unit; in heating, it reverses and pulls heat out of that water. The building’s cooling tower and boiler keep the loop in range.
How much does it cost to replace a water source heat pump?
We quote it monthly and installed. From about $152 a month at 0% APR for 60 months, the whole price financed, on approved credit. Installed, it’s $9,100 to $10,300, in the same closet or ceiling space, with the valves and hoses checked and a sound blanket where the closet is next to a bedroom.
What is a vertical stack heat pump?
A water source heat pump built as a tall, narrow cabinet with the building’s risers running through it, stacked floor over floor. Its working part is a chassis that slides out, so a replacement is often a new chassis in the old cabinet, with no drywall opened.
What’s the difference between a water source heat pump and geothermal?
The water. A geothermal heat pump’s loop runs through the ground or a well; a condo’s runs through a cooling tower and a boiler. The same models are often sold for both, rated at different water temperatures.
Who is responsible for a water source heat pump in a condo?
Your declaration decides. Where it’s silent, Virginia Code section 55.1-1912 makes anything that serves only your unit part of your unit, and section 55.1-1955 makes its upkeep yours. That usually puts the heat pump, its thermostat and its drain line on you, and the risers, cooling tower and boiler on the association. The valves and hoses are where buildings differ most.
How long does a water source heat pump last?
ClimateMaster cites ASHRAE for more than 20 years on these systems. Clean loop water, a clean strainer, hoses that get checked and a filter changed on time are what get a unit there.
Why is my water source heat pump blowing room-temperature air?
Usually a safety lockout: the compressor stopped because the water flow dropped, the loop drifted out of range or the filter clogged, and the fan kept running. Check the filter, switch the breaker off and on once, and ask the building about the loop. If it locks out again, call (703) 997-9757.
Does a new water source heat pump use R-454B?
Most new ones use R-454B (ClimateMaster’s and Trane’s) or R-32 (Daikin’s newer units), because the EPA capped refrigerants for this equipment at a global warming potential of 700 for units built from 2025. An existing R-410A unit can still be repaired with R-410A.
Water source heat pump service and replacement in Northern Virginia
Call (703) 997-9757, or book on our condo HVAC page. Have a photo of the data plate ready, and the name of your building’s engineer or management office. Or send the form at the top of this page and the office calls or texts you back.
SwiftPro Heating, Cooling & Plumbing repairs and replaces heating and cooling systems across Northern Virginia, from Chantilly and Ashburn, condo systems included: water source heat pumps, First Co and Aquatherm units, MagicPaks and fan coils, with a dedicated HVAC team and a separate plumbing team. Trane Comfort Specialist, Rheem Pro Partner, Carrier experts and Mitsubishi Electric Diamond Contractor. Family owned, BBB Accredited with an A rating, 24/7 emergency service, Virginia Class A contractor license 2705192276, and rated 5.0 stars across 1,132 reviews on Google, Angi, Yelp, the BBB and Facebook. Read the reviews.
