Tankless Water Heaters
On-demand gas units supplied and installed. Navien NSS certified, so commissioning is done to manufacturer spec and the warranty stands.
Plumbing
Water Heater Installation & Replacement On Long Island
Tankless, gas and electric water heaters installed and replaced by a licensed Long Island team. NJM is Navien NSS certified, so high-efficiency and tankless systems are installed to spec and your warranty stays intact.
TANKLESSGAS & ELECTRICNAVIEN NSS CERTIFIEDFREE ESTIMATES
Licensed & Insured
Master Plumber
TASK 86/87 Certified
Navien NSS Certified
22+ YEARS ON LONG ISLANDGet Your Free Estimate
LICENSED & INSURED · NASSAU & SUFFOLK
PLUMBING · HEATING · COOLING · CONTRACTING
Have An Emergency? We’re Available 24/7.
631-587-0085WE ANSWER EVERY CALLPlumbing
Water Heater Installation & Replacement On Long Island
Most people replace a water heater in a hurry, because most water heaters announce their retirement by flooding a basement. That urgency is exactly why the wrong unit gets installed — whatever the supplier has in stock, sized to match the old one, connected as quickly as possible. NJM installs tank and tankless water heaters across Nassau and Suffolk County, and we would rather have the sizing conversation with you before the old one fails.
We are Navien NSS certified, which matters for high-efficiency and tankless equipment: factory-trained installation is what keeps the manufacturer warranty intact and what determines whether a tankless unit actually delivers the flow rate it is rated for. We are also TASK 86/87 certified, so the gas side is handled by the same licensed crew rather than subcontracted.
24/7 Emergency ServiceLicensed & Insured
Master PlumberLicensed to pull permits
TASK 86/87Certified for gas work
Navien NSSFactory-trained on tankless
22+ years on Long Island · Plumbing, heating, cooling, gas and contracting under one roof
What We Install
Water Heater Services
Gas Water Heaters
Conventional tank units installed and replaced, with the gas connection and venting handled by TASK 86/87 certified staff.
Electric Water Heaters
Tank and point-of-use electric units for homes and businesses where gas is not available or practical.
Emergency Replacement
A failed water heater usually means water on the floor. We answer 24 hours a day, every day of the year.
Gas Line Upgrades
A tankless conversion often needs more gas than the existing line can carry. We do that work in-house rather than sending you to another contractor.
Venting & Combustion Air
Correct venting for high-efficiency and conventional units — a common failure point in quick replacements.
Commercial Water Heating
Higher-demand systems for restaurants, multi-family properties and businesses across Long Island.
Sizing & Assessment
Sized from how the household actually uses hot water rather than by matching whatever was there before.
Plumbing — before you call
Two kinds of visit. You’ll know which before we come.
We don’t charge to quote a job. We do charge to find a problem nobody has identified yet. Which one you need — and what it costs — gets agreed on the phone, so nothing about the cost is a surprise on the doorstep.
The rate you are told is the rate
You get the number on the phone, before anyone is dispatched, and it is what you are charged when the technician arrives. One rate across all four trades — plumbing, heating, cooling and gas.
What it pays for
A licensed, insured technician carrying the certifications the work needs, and the time to find what has actually failed — not a quick look and a guess.
Watch for the bait and switch
A call-out advertised at almost nothing gets recovered once someone is standing in your basement. Get the number before anyone travels — from us, or from anyone else you call — and hold them to it when they arrive.
Financing on larger jobs
A boiler that fails in January is not a purchase anyone planned. Financing is available on the big-ticket work, so a system replacement does not have to come out of savings in one go.
What it is normally used for
Boiler, furnace and water heater replacement, a full air conditioning system, a whole-house repipe, sewer and water main work, and larger contracting jobs — kitchens, bathrooms, dormers and extensions.
When to bring it up
At the estimate, before anything is scheduled. It is worth asking even if you think you will not need it, because knowing it is there changes what you are willing to consider fixing properly.
What it does not change
The price of the job. The quote is the quote whether you finance it or not — and on a straightforward repair it is usually not worth the paperwork. We will tell you which one you are looking at.
Financing provided throughSynchronyCredit is extended by Synchrony. Subject to credit approval.
Call 631-587-0085Not sure which one you need? Call and describe it — we will tell you before we book anything.
Common Faults
What Usually Goes Wrong
The calls we take most often, and what is generally behind them.
No Hot Water At All
On gas, usually the pilot, thermocouple or gas control valve. On electric, usually the upper element or a tripped high-limit reset behind the panel. On a tankless it is normally an error code, which is worth reading before anything gets replaced.
Runs Out Too Fast
A broken dip tube, sediment eating the usable capacity, or a tank that is simply undersized for how the house uses water now. Adding a bathroom without resizing the heater is the usual story.
Not Hot Enough
Thermostat setting first, then a failed lower element on electric, then sediment insulating the burner from the water it is meant to be heating.
Rusty Or Discoloured Water
Often the anode rod has done its job and is spent. Sometimes it is the tank itself going. Worth diagnosing quickly, because a corroded tank does not fail gradually.
Banging Or Rumbling
Sediment. Long Island water builds it up fast, and the noise is water trapped underneath it boiling. Not urgent on its own, but it costs efficiency and shortens the tank life.
Water Around The Base
Could be the temperature and pressure relief valve, could be a fitting, could be the tank. Only one of those three is a cheap fix, and it is not worth guessing which.
Pilot Will Not Stay Lit
Most often the thermocouple. Sometimes a blocked flue or a draught problem, which matters considerably more than the pilot does and is the reason this one gets looked at rather than relit.
Ten Years Or Older
Not a fault, a warning. Most tanks last eight to twelve years on Long Island water. Replacing one on a Tuesday you chose costs less than replacing it on a Sunday it chose.
Tank Or Tankless
Which One Actually Suits Your House
Tankless is not automatically better. It heats water on demand rather than keeping a tank hot, which removes standby losses and means you do not run out — but it costs more up front, often needs a larger gas supply and different venting, and its performance is measured in flow rate rather than gallons. A house running two showers and a dishwasher at once needs a unit sized for that, or somebody gets a cold rinse.
A conventional tank remains the right answer in plenty of Long Island homes, particularly where gas supply or venting would make a tankless conversion disproportionately expensive. What decides it is your hot water pattern, the existing gas line, the venting route and where the unit has to sit — and in a basement with flood history, a wall-mounted tankless has an advantage that has nothing to do with efficiency.
Quick Rules Of Thumb
- Tankless never runs out, but is rated by flow rate, not capacity
- A tankless conversion often needs a larger gas line and new venting
- Wall-mounted tankless sits above shallow flooding — relevant on the south shore
- A conventional tank is still the better value in many houses
- Sizing from your actual hot water usage, not from the old unit’s label
Trusted Equipment
Brands We Install & Service
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Everything We Handle In Plumbing
One licensed team, one number to call, across Nassau and Suffolk County.
Current Offers
Money Off, Plainly Stated
What it says on the coupon is what comes off the bill. Mention it when you call.
$50 Off
Water Heater Repair
Cold shower this morning. Fifty dollars off getting the hot water back.
Code NJM-WHREP50Expires October 31, 2026See the details →$100 OffWater Heater Replacement
Most tanks last eight to twelve years on Long Island water. Replacing one on a Tuesday you chose costs less than a Sunday it chose.
Code NJM-WH100Expires October 31, 2026See the details →$200 OffTankless Water Heater Installation
Navien NSS certified, so commissioning is done to manufacturer spec and the warranty stands.
Code NJM-TANK200Expires October 31, 2026See the details →Common Questions
Frequently Asked Questions
How long does a water heater last?
A conventional tank typically gives eight to twelve years, and tankless units generally longer with maintenance. Rusty hot water, rumbling from the tank, or any moisture around the base are the signals that it is near the end. A tank that is weeping is going to fail, not recover.
Is tankless better than a tank?
Not automatically. Tankless never runs out and removes standby losses, but it costs more up front and is rated by flow rate rather than gallons — so it has to be sized for how many fixtures you run at once. It also often needs a larger gas line and different venting. In plenty of Long Island houses a conventional tank is still better value, and we will tell you when that is the case.
What size water heater do I need?
It depends on your actual hot water pattern — how many bathrooms, how many people, whether showers and appliances overlap. Sizing by matching whatever was there before just repeats whatever was decided last time, which may well have been wrong.
My water heater is leaking. Can it be repaired?
If the leak is from a fitting, a valve or the temperature and pressure relief, often yes. If the tank itself is weeping, no — that is corrosion through the tank wall and it will fail completely. Turn off the water supply to the unit and call 631-587-0085.
What does Navien NSS certified mean for me?
It means we are factory-trained on Navien condensing and tankless equipment. Practically, that matters for two things: the unit is commissioned to manufacturer spec so it performs as rated, and the manufacturer warranty is not compromised by the installation.
Can I convert from a tank to tankless?
Usually, but it is rarely a like-for-like swap. Tankless typically needs a larger gas supply and a different venting arrangement, so the honest cost includes that work. We do the gas and venting in-house, which is why we can price the whole thing rather than quoting the unit and discovering the rest later.
Do you offer financing?
Yes. This is the kind of job most people are not expecting to pay for all at once, particularly when the old one has just failed. Financing lets the work happen when it needs to rather than when the savings catch up. We finance through Synchrony, subject to credit approval. Ask when you call and we will go through the options for your job.
Do you handle emergency water heater replacement?
Yes, 24 hours a day, every day of the year. A failed water heater usually means water spreading across a basement floor, which is not a next-week problem. Call 631-587-0085.
Are estimates free?
Yes, free and with no obligation. Call 631-587-0085, or use the form on this page and we will be in touch within 24 hours.
Service Area
Proudly Serving Long Island and Surrounding Areas.
Based in North Babylon, working across both counties — close enough to get there fast, local enough to know the housing stock and the permit offices.
Find Plumbing Services Near You!
- Long Island
- Nassau County
- Suffolk County
Towns We Serve
- North Babylon
- Babylon
- West Babylon
- Deer Park
- Lindenhurst
- Farmingdale
- Massapequa
- Hicksville
- Dix Hills
- Commack
- Islip
- Hempstead
- North Hempstead
- Rockville Centre
Proudly serving all of Nassau and Suffolk County, with deep local roots near our North Babylon home base.
Get A Free EstimateWhat Long Island Says
Reviews From Homes & Businesses We've Served
5 out of 5 stars
Hot water heater went down Neil from NJM was on the job asap and had me back up and running with new system in 24 hours. Quality of work was top notch . Highly recommend Neil and his team. Thank you Neil
Bryan BlancoJanuary 2026
5 out of 5 stars
Neil was great and takes the time to explain everything in detail including the pricing. Used him and his company for a Navien tankless install and he got it done in 2 days staying late each day to ensure that we had heat and hot water on the second day. Would recommend him and his company wholeheartedly
Terry KossegiOctober 2025
5 out of 5 stars
I contacted NJM Mechanical because I didn't have hot water anywhere in my house. Neil was able to diagnose the issue and get to work. My navien tankless water heater is only a year old and still under warranty. Instead of waiting on Navien to send the part so the issue can be corrected, Neil went out, found the part, purchased it, and fixed the issue. Happy to report we have hot water again. Thank you Neil.
Justin BlackmanApril 2025
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