Summary:
On the East End, pool season ends quietly. Labor Day passes, the pool gets closed, and for a few weeks the weather stays mild enough that nobody thinks about the equipment pad behind the pool house. Then the first hard freeze arrives, often before anyone has been back to look.
A propane pool heater is the piece of pool equipment that a freeze can hurt most. This guide explains what happens when water freezes inside one, the order the winterizing work should follow, and which parts of it belong to a technician. It is written for homeowners who rely on a propane company in Quogue, where many pools sit at second homes that stay closed from September to spring.
What Freezing Water Does to a Heat Exchanger
The heart of a pool heater is its heat exchanger, a bank of tubes, usually copper or a copper alloy, that carries pool water through the heater while the burners warm it. Those tubes, and the headers that connect them, are built to hold water under pump pressure. They are not built to hold ice.
Water expands by roughly 9 percent as it freezes. Inside a closed tube there is nowhere for that expansion to go, so the ice pushes outward until something gives. The usual result is a split tube or a cracked header, and the damage is often invisible from outside the cabinet.
That is what makes it the expensive failure. A cracked heat exchanger generally means replacing a major part, and sometimes the whole heater, and it tends to be discovered only in spring, when the pump starts and water appears under the unit. It is also almost entirely preventable, which is the whole point of pool heater winterization before the cold sets in.
The Winterizing Steps, in the Right Order
Winterizing a pool heater is not complicated, but the order matters. Each step sets up the next, and skipping ahead is how water gets left where it should not be.
First, the heater is shut down. That means turning it off at its controls, switching off its electrical supply, and having its gas supply shut off. The first two are simple. The gas shutoff is a technician’s job, and the section on the gas side below explains why.
Second, the heater is drained. With the pump off, the drain plugs on the heat exchanger header come out and the water runs out of the heater. Some heaters have more than one drain point, and some only empty fully once the water connections at the inlet and outlet are opened. The heater’s manual shows where they are on your model.
Third, the water lines are cleared. The plumbing between the pump, the filter and the heater holds water too, and any left in a low spot can freeze and crack a pipe or fitting. The lines are usually blown out with air and plugged at the pool, often as part of closing the pool.
Fourth, the plugs stay out. The drain plugs are left out all winter so any water that collects can escape. Keep them where you will find them in spring, such as a labelled bag tied to the heater.
Fifth, the heater is covered. A cover keeps out leaves, snow and nesting animals, but it should not seal the cabinet airtight, because trapped moisture causes corrosion. Follow the manufacturer’s guidance on the top vent.
In Quogue, where many pools are closed by a pool service soon after Labor Day, it is worth confirming that the heater was actually drained, not just switched off.
Why Draining Beats Antifreeze in the Heater
Pool antifreeze is a common part of closing a pool, and it has a real place. It goes into the water lines after they have been blown out, as insurance against any water left sitting in a low spot. That leads some owners to assume it belongs in the heater too. In most cases it does not.
The heater is a different situation from the pipes. A heat exchanger can be drained almost completely, and a drained heat exchanger has nothing in it to freeze. That is better protection than any fluid, and it is the method heater manufacturers generally call for.
Antifreeze in the heater also brings problems of its own. Some manufacturers advise against putting it in the heat exchanger at all, so check your manual before adding any. Pool antifreeze is also diluted by whatever water is still in the system, so a heater that was only partly drained and then topped up may not be protected at the strength the label suggests. And whatever goes into the heater in the fall gets flushed into the pool in the spring.
The safer approach is to drain the heater fully, leave the plugs out, and use antifreeze, if at all, only where your pool professional recommends it in the plumbing. If your heater’s manual says something different, follow the manual. It is written for your model, and this guide is not.
The one thing not to do is assume a heater with water in it will be fine because the fall has been mild. On the East End, a single hard night in late November or December is enough to do the damage, and it often follows a stretch of warm weather that made the job feel unnecessary. A heater that was drained in October does not care when the cold arrives.
The Gas Side Is a Technician’s Job
A propane pool heater is not just plumbing. It is a gas appliance with burners, a gas valve, an ignition system and a vent, connected to a propane supply line. Shutting it down properly for the winter includes the gas side, and that part is work for a qualified technician, not a homeowner.
Please do not disconnect, loosen or adjust any gas line, fitting or valve on the heater yourself. A technician shuts off the supply correctly, checks the connections for leaks, and looks over the burners and venting for the corrosion, debris and nesting that build up over a season. In spring, the technician restores the gas side and checks for leaks before the heater is relit.
If you ever smell gas near the heater or the tank, do not operate switches or equipment nearby. Move well away first, then call your propane supplier or 911. Our installation and service team handles this side of the work.
What Homeowners Can Do, What Technicians Do
Some pool heater winterizing is well within reach of a careful homeowner, and some is not. Knowing where the line falls saves trouble on both sides.
On the homeowner side are turning the heater off at its controls, switching off its electrical supply, removing the drain plugs, letting the heat exchanger empty, storing the plugs and putting on a breathable cover. Clearing leaves and debris from around the cabinet, and making sure sprinklers do not spray onto it, are simple and worthwhile too.
On the technician side is everything involving the gas supply, the burners, the gas valve, the ignition and the venting. A technician will also look for problems that are easier to catch in the fall than the spring: soot on the burners, a corroded burner tray, a damaged vent cap, or signs that mice have moved into the cabinet. Salt air near the bays and the ocean speeds up corrosion on heater cabinets and burner parts, so a yearly look matters more on the coast.
The water lines sit in between. Many owners leave blowing them out to their pool company, because a poor job can leave water in pipes that look drained but are not.
For Quogue homeowners who close the house in September, the practical answer is often to have professionals do the whole job and confirm it was done. If a caretaker checks the property over the winter, show them where the heater is and what it should look like: plugs out and covered. The same fall visit is also a sensible time to have the house’s side of the system looked at, and our propane home heating services cover the furnace and boiler.
What Happens to Your Tank Over Winter
A pool heater is one of the biggest propane loads a house can have. While it runs, it can burn fuel far faster than a furnace on a mild day, which is why summer usage at a home with a heated pool can look so different from the rest of the year.
Once the heater is shut down, that load comes off. What happens next depends on how the tank is set up.
If the pool heater shares a tank with the house, usage drops to whatever the furnace, water heater, range and fireplace need. At a home lived in year-round, the furnace soon becomes the main load. At a second home with the heat turned down to protect the pipes, usage may fall to a trickle, but it does not stop, and a tank nobody is watching can still run low by spring. Our guide to how long a propane tank lasts explains how to estimate it.
If the pool heater has its own tank, that tank will usually sit unused until spring. There is nothing wrong with that, but it is worth knowing how much is in it so the first heat-up of the season does not catch you short. The LP tank sizes and capacity chart shows what common tanks hold.
Either way, tell your propane supplier when the pool heater goes off for the season. On automatic delivery, fills are planned around how much you use, and a big drop changes that picture. If you order deliveries yourself, check the gauge before you close the house and arrange propane delivery if it is getting low, so the house is not left on a thin margin all winter.
Closing Up a Quogue Pool for Winter
Quogue’s pools face a particular version of the winter problem. Many sit at second homes that are closed after Labor Day and left empty through the freeze, so a heater that was not drained may not be noticed until the pool is opened in spring and the damage shows. Properties along Quantuck and Shinnecock bays and out on Dune Road also take more wind and salt air than inland yards, which is hard on any equipment left outside.
The plan is simple. Have the heater shut down, drained, cleared and covered before the first hard freeze, with the gas side handled by a technician. Check the tank before you leave, and let your supplier know the pool load is off.
Liberty Gas serves homes and businesses in Quogue and across Suffolk County from 225 Old Riverhead Rd in Westhampton Beach. To ask about winterizing your propane pool heater, call 631-288-0902, or request a propane delivery online before you close up the house.
