No hot water: what to check before you call a plumber

No hot water is one of the few plumbing faults where five minutes of looking, before anyone comes out, genuinely changes the outcome. Sometimes it fixes it. More often it tells you which part has failed, which means the right parts arrive on the first visit instead of the second.

Here is what to check, in the order worth checking it, and what each answer rules out.

First: is it no hot water everywhere, or one faucet?

This single question splits the problem in half, so answer it before anything else.

• One faucet only. Not a water heater problem. It is that fixture — a failed cartridge in the faucet, a seized shut-off valve under the sink, or a blocked aerator on the hot side.
• One bathroom, everything else fine. Usually a valve feeding that branch, or a thermostatic mixing valve that has failed closed on the hot side.
• The whole house. Now it is the water heater, the boiler, or the fuel and power getting to them.

If it is the whole house, check these four things

In order. Each takes a minute and each rules something out.

• Is there power or gas to it? A tripped breaker or a switched-off service switch beside the unit is the single most common cause of no hot water that turns out to be free. Check the breaker panel, and check the switch on or near the heater itself — it looks like a light switch and gets knocked.
• Is the pilot or ignition lit? On an older gas heater there is a sight glass near the bottom. No flame means either it has gone out or the thermocouple has failed, and those are different repairs.
• Is there water on the floor around it? If yes, stop reading and shut the water off to it. A leaking tank is not a repair, and the longer it runs the more of the floor goes with it.
• How old is it? There is usually a date in the serial number on the label. Past about twelve years, money spent on a repair is money spent twice.

What the pattern tells you

If there is some hot water but not enough, the unit is working and something else is wrong. The pattern is the clue:

• Hot, then suddenly cold, much sooner than it used to be. Classic failed lower element on an electric heater, or sediment filling the bottom of the tank and stealing its capacity.
• Lukewarm everywhere, never properly hot. A thermostat, or on an electric unit one of two elements gone — you get roughly half the heat and half the recovery.
• Hot at the kitchen, cold upstairs. Usually a crossed connection or a failed mixing valve rather than the heater.
• Cold for twenty seconds, then fine. That is just the length of the pipe run. Not a fault.
• Rumbling or knocking from the tank. Sediment. It is also why the unit costs more to run every year.

When no hot water is actually a heating problem

In a lot of older houses around here the hot water is made by the boiler rather than by a separate tank. If that is your setup, then no hot water and no heat arrive together, and the thing to fix is the boiler — boiler repair rather than water heater repair.

The quick test: if the radiators are cold as well, it is the boiler. If the radiators are hot and the faucets are not, the boiler is running and the fault is in the hot water side of it.

No hot water in a two-family or an apartment

This is its own situation, and it is common in Yonkers and in the apartment stock around White Plains. Before assuming it is your problem:

• Ask the neighbors. If the other units have no hot water either, it is a shared system and the building’s problem, not yours.
• Find out whether your unit has its own heater. In a lot of converted two-families each apartment has one, often in a closet or the basement, and the tenant has never been shown where.
• If it is a shared system, the landlord or managing agent has to make the call. We provide a certificate of insurance before entering a building, which is usually the thing that holds that up.

What not to do

• Do not turn the thermostat on a water heater right up to compensate. It will not fix a failed element and it will scald someone.
• Do not relight a pilot repeatedly if it will not stay lit. If it goes out twice, something has failed and relighting it is not the fix.
• Do not ignore a smell of gas. Leave, then call the gas utility from outside. That one is not a plumbing job until they have made it safe.
• Do not drain a tank you think is leaking without knowing where the shut-off is first.

When to call

Call if there is water on the floor, if the pilot will not stay lit, if the unit is over about twelve years old, or if you have no hot water and no heat at the same time. Call straight away if you smell gas, and call the gas utility first. For anything that cannot wait until morning, an emergency plumber is what you need, and the phone is answered.

If the answer turns out to be replacement rather than repair, that conversation includes whether a tankless water heater actually suits your gas supply — because sometimes it does not, and we would rather say so before you buy one.

KBD Plumbing & Heating works across lower Westchester — Dobbs Ferry, Hastings-on-Hudson, Irvington, Yonkers, White Plains and the rest. Licensed and insured, price agreed before work starts, and the phone is answered any hour including holidays: (914) 233-3000.

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