Running out of hot water occasionally is annoying.
Running out of it regularly in a large household usually means the hot water system simply isn’t keeping up with demand.
That was the problem at this property.
It’s a large seven-to-eight-bedroom home, and the existing hot water setup wasn’t providing enough capacity for the amount of hot water being used. With multiple people showering, washing, cleaning and using hot water throughout the day, they were regularly reaching the limit of what the system could provide.
So we went bigger.
A 400-Litre Thermann Hot Water System
RJT Plumbing & Gas installed a 400-litre Thermann storage hot water system to give the property considerably more available hot water.
For a large household, storage capacity matters.
Every shower, bath, sink and hot-water appliance draws from the same available supply. If several people use hot water one after another, a smaller storage system can be depleted faster than it can recover.
Once that happens, somebody ends up with a cold shower.
With a 400-litre storage tank, this home now has a much larger reserve available before the system needs to recover.
The result?
They were always running out of hot water. Not anymore.
Why Large Homes Can Struggle With Hot Water
A hot water system that works perfectly well for two or three people may be completely unsuitable for a much larger household.
Hot water demand can increase quickly when you’ve got:
- multiple bathrooms
- several showers being used each morning or evening
- larger families
- guests or extended family living in the home
- baths
- dishwashing and cleaning happening at the same time
- high overall household water use
The number written on the side of the tank is only part of the equation.
When we’re looking at a hot water problem, we also consider when the household uses its hot water.
A home where everyone showers at different times has a very different demand profile from a home where six people are trying to get ready between 6:00am and 8:00am.
That’s why correctly sizing a hot water system matters.
Is a Bigger Hot Water System Always Better?
Not necessarily.
Installing the biggest tank available isn’t automatically the right solution.
A properly sized system needs to balance:
- household size
- number of bathrooms
- typical shower use
- peak hot water demand
- available installation space
- energy source
- recovery rate
- existing plumbing
- household routines
An oversized system may store more hot water than a smaller household ever needs.
An undersized system creates the opposite problem: not enough hot water when everybody actually wants to use it.
For this property, the recurring lack of hot water made it pretty clear that greater storage capacity was needed.
Storage Capacity and Recovery Rate Both Matter
When people say their hot water system is “too small”, they’re usually talking about how quickly they run out.
But there are actually two important parts to the equation.
Storage capacity
This is how much hot water the tank can hold ready for use.
A larger storage system gives the household a bigger reserve.
Recovery
This is how quickly the system can heat replacement water after hot water has been used.
If household demand regularly exceeds both the available storage and the system’s ability to recover, you’ll eventually run out.
For large households, getting both parts of the equation right can make an enormous difference to everyday comfort.
Signs Your Hot Water System May Be Undersized
Regularly running out of hot water is the obvious sign, but there are a few patterns worth watching for.
You might notice:
- the first few showers are hot but later showers aren’t
- hot water disappears at roughly the same time every morning
- the problem gets worse when guests stay over
- baths use most of the available hot water
- you’re constantly organising who can shower and when
- the system works normally during quiet periods but struggles during peak use
If that sounds familiar, the problem might not be a fault with the system.
It may simply be that the system no longer matches the household using it.
Hot Water Systems Should Be Sized Around the Home
Hot water requirements can change over time.
A system installed years ago may have originally been perfectly suitable, but things change.
Families grow. Bathrooms get added. Homes are renovated. More people move in. Water-use habits change.
The original hot water system can eventually become the bottleneck.
That’s why replacing a hot water system isn’t just about finding another unit with similar dimensions.
It’s an opportunity to ask whether the old system was actually doing the job properly in the first place.
Need More Hot Water?
If you’re constantly running out of hot water, RJT Plumbing & Gas can assess your current system, household demand and available options.
Sometimes the answer is repairing an existing system.
Sometimes it’s improving the setup.
And sometimes, as with this seven-to-eight-bedroom home, you simply need a lot more hot water available.
This one now has 400 litres of it ready to go.
No more organising showers around the hot water system.
No more being the unlucky person who goes last.
Problem solved.
Frequently Asked Questions
Why does my household keep running out of hot water?
A household can run out of hot water when demand exceeds the storage capacity or recovery rate of the hot water system. This is especially common in larger homes with multiple bathrooms or several people showering within a short period.
Is a 400-litre hot water system suitable for a large family?
A 400-litre storage hot water system can be suitable for a large household with high hot water demand, but the correct system size depends on household size, bathrooms, usage patterns, available space and the system's recovery rate.
How do I know if my hot water system is too small?
Common signs include hot water running out during consecutive showers, later showers becoming cold, shortages occurring at the same time each day, or the system struggling whenever several people use hot water close together.
Does a larger hot water tank mean I will never run out of hot water?
A larger tank provides more stored hot water, but recovery rate and household demand are also important. A correctly sized system should balance storage capacity with how quickly the household uses and replaces hot water.
What should be considered when sizing a hot water system?
Important factors include the number of people in the home, number of bathrooms, shower and bath usage, peak demand times, available installation space, energy source, recovery rate and existing plumbing.
Can a hot water system become too small as a household changes?
Yes. A hot water system that once suited a property may become undersized if the household grows, extra bathrooms are added, usage patterns change or more people begin living in the home.
Can RJT Plumbing & Gas help with hot water system sizing?
Yes. RJT Plumbing & Gas can assess an existing hot water system, household demand and installation requirements to determine whether repair, adjustment or a larger replacement system is the most practical solution.
