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Guide to Instant Gas Hot Water Problems
gas hot water problem guide

Guide to Instant Gas Hot Water Problems

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Many of today’s homes and commercial spaces are using gas hot water systems. That said, it’s important for them to know some of the most common gas hot water system problems to help them identify which problem is which and how to fix them.

Common Gas Hot Water Problems That Occur

Lukewarm water

One of the most common issues on tankless water heaters is having lukewarm water.

There are a couple of reasons why this might happen but there’s a good chance that it’s because the thermostat sits at a low setting or it could be faulty. A fix for the former is simply to adjust the setting while the latter may require the help of a professional plumber.

In some cases, the system’s flow rate is unable to keep up with your home’s hot water demands. If this is the reason, you can adjust your family’s hot water usage and make sure that not everyone is using hot water at once.

Should this workaround may not be convenient for you and your family, you can always get a larger heater or install an additional unit to work in conjunction with your existing instant gas hot water heater.

No hot water

Sometimes, the water you get from your faucet and showers isn’t hot at all. Like lukewarm water, there are several reasons why this could happen.

To isolate the issue, you can start by checking if your instant gas hot water system is plugged in and turned on at the power outlet. If you find that it isn’t, simply plug it in and boot it up. Otherwise, you can check your gas connection.

This next step entails looking at other gas appliances you have at home. Check if they’re working. If they are, it could mean that you have a problem with your gas connection and that you’re going to need the help of a qualified gas fitter. If they aren’t, there’s a good chance that you need to call your gas provider.

Intermittent hot and cold water

Sometimes, your continuous flow gas hot water system may start acting up and you could get both hot and cold water intermittently.

When this happens, it could mean that the diaphragm on the gas meter could be faulty or there’s not enough gas on your hot water system.

Plumbers also report that some houses have faulty shower heads or a restrictor may be affecting the tap’s ability to be read as a hot water tap.

Either way, you will need to ask the help of a professional plumber.

Mineral build up

Another problem encountered by tankless water heater users is mineral build up. This happens when minerals in the water begin to build up inside the heater causing scales and hardened accumulation. This can severely impact how efficient the heater works.

When this happens, you will have to flush the water more often to avoid the water sitting in the heater.

Low water pressure

In addition to periodically getting cold and hot water, other instant gas hot water users say that they also sometimes experience low water pressure.

According to professionals, low water pressure could be caused by a blocked cold inlet strainer valve which in turn reduces the amount of water coming from the instant water heater.

There’s also a chance that your thermostat may be broken or faulty.

Like intermittent hot and cold water, you will also have to call in a plumber to help you fix low water pressure.

Fortunately, you can always rely on one of Melbourne’s best plumbing companies — Zabs Plumbing.

We handle anything including general plumbing, bathroom renovations, gas fitting and repairs, gas heater services and repairs, residential plumbing, new homes and renovation, roof and gutters, commercial plumbing, hydronic heating, and of course, hot water services and repair.

Our company also specialises in blocked drains, emergency plumbing, drain inspections, and gas heating.

At Zabs Plumbing, we are backed with 18 years of experience and can help you with a variety of problems with your instant gas hot water heater. We are backed by fully licensed, insured, and high-quality plumbers who can help you 24 hours a day seven days a week.

Ignition failure

Sometimes, the reason why your instant gas hot water heater is not working as it should is that it failed to ignite in the first place. More often than not, the problem starts with your gas supply. That said, make sure to check your propane tank and ensure that it’s full before doing anything else.

You would also want to check if the gas valves are fully opened as it can also cause problems with your pilot light.

Experts say that if the above steps did not resolve the problem with your tankless heater, then there’s a chance that your ignition pack has failed — or it could be a sign that there’s a bigger problem.


Because instant gas hot water heaters are now common on most homes and commercial buildings, it’s important that homeowners and property managers know how to deal with these issues.

While some of them can be fixed with simple steps, others may require the help of a plumbing professional. If you haven’t found a plumber yet, contact us today.

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