Can You Fill a Hot Tub With Garden Hose Water?


The water that comes out of a hose isn’t exactly sparkling clean, and the last thing you want to do is damage your hot tub. So is it safe to fill a spa using water from a garden hose?

It’s safe to fill a hot tub using water from a garden hose pipe. For most homeowners, it’s necessary to connect an inexpensive pre-filter to the end of the hose to filter out any impurities in the water. The correct technique needs to be used in order to avoid airlocks which can lead to heater failure.

Later on, I’m going to show you how to avoid unsanitary water and potential damage such as airlocks by using the correct filling technique with your garden hose.

Using hose water to fill a hot tub

Using hose water is the most convenient way to fill a hot tub. It’s easier and safer than attaching a hose to a kitchen sink faucet and having it run through the house, creating a trip hazard.

There’s no need to be concerned about the quality of the water that comes from your outside faucet. While you wouldn’t want to drink it, it’s perfectly safe for your hot tub.

In fact, the water that comes from an outside faucet is often ideal as it won’t have been softened.

You shouldn’t fill your entire hot tub with water filtered by a water treatment system. The soft water may be great to drink, but it will damage the spa shell and its components.

The good news is that most water softening systems don’t treat the water coming from the outside faucet, so you don’t need to worry.

But before you rush out to fill up your hot tub using the garden hose, there is one accessory you need to prevent problems.

Attach a pre-filter to your hose

Attaching a pre-filterOpens in a new tab. to the end of the hose is absolutely essential when filling your hot tub with hose water.

Water from your garden hose is unlikely to be filtered, meaning it may contain residual metals and contaminants. The harder the water where you live, the more impurities it contains.

Impurities such as copper, calcium, sodium, iron, and other heavy metals can be harmful to you and your spa’s components.

A build-up of calcium causes scaling and prevents sanitizing chemicals from working properly, exposing you to nasty bacteria that can make you sick.

By connecting an inexpensive pre-filter, you can remove up to 98% of the impurities in the water. The pre-filter attaches to the end of the hose and is good for filtering around 1,200 gallons (4,542 liters) of water.

Removing the impurities makes it easier to balance the water chemistry too, meaning that you can use fewer chemicals.

Some 15 million households in the US rely on private water wells. Well water is particularly hard, so it’s well worth mentioning that pre-filters are a must if you’re going to be filling your spa from a well.

So unless you live in an area with extremely soft water, do yourself a favor and attach a pre-filter. Honestly, I’d have one fitted even if my water was soft as it can’t do any harm.

Where to place the hose when filling a hot tub to avoid airlocks

A mistake that a lot of hot tub owners make is to cause an airlock by placing the hose in the footwell when filling with water.

An airlock is an air bubble that gets trapped within the plumbing as it’s filling with water. They can be extremely damaging, causing something known as “dry firing.”

Dry firing causes instantaneous heater failure. When air is trapped in the plumbing, the pump’s motor burns up. Dry firing is not covered under warranty, and it’ll cost you quite a bit of money to repair or replace.

To reduce the risk of air bubbles, place the hose inside the filter well instead. Once the hot tub is full of water, you’ll need to prime the pump to make absolutely sure there is no air in the plumbing.

Priming the pump pushes out any air, enabling the water to flow through the pipes. Priming is necessary every time you fill your hot tub.

How you’ll prime your spa’s pumps depends on the model you own. Some have a self-priming mode that you can activate from the control panel, while others require you to carry it out manually using a bleeder valve.

How long does it take to fill a hot tub with a hose?

Filling an average-sized hot tub containing 300 gallons takes approximately 1.5 to 2 hours. The rate at which your hot tub fills will depend on factors such as water pressure, water flow rate, hose size, where you live, and the time of day.

Standard hoses are usually 3/4”, but they’re available in much wider diameters. By using a hose with a 2” diameterOpens in a new tab., you can dramatically speed up the time it takes to fill up your spa.

Of course, the size of your hot tub will determine the amount of time it takes to fill. Because no one wants to stand there watching a hot tub fill, I’ve created a handy table with approximate times based on typical water pressure and flow rates.

Capacity (gallons)Time to fill (slow: 2.5 gal/min)Time to fill (fast: 3.3 gal/min)
1506045
30012090
500200150
700280210
Time (in minutes) to fill different sized hot tubs

Everyone’s water source is different, and it even fluctuates at different times of the day, so it’s a good idea to measure the water flow from your outside faucet. It’s simple enough to estimate the time it’ll take to fill by using my handy guide.

Overfilling your hot tub can cause huge amounts of damage, which is why I recommend using a hose timerOpens in a new tab.. Once you’ve calculated the fill time, you’ll never have to worry again as the timer will shut the water off automatically.

What should the water level be in a hot tub?

You must fill your hot tub to the minimum fill line to ensure that it functions properly. The maximum fill level is 2 to 3 inches (50 – 75mm) above the top of the filter and an inch (25mm) below the headrests. Do not fill any higher to avoid overflow as the water level will rise as people enter the spa.

You would think that all hot tubs were completely watertight, but unfortunately that’s not the case. Accidentally overfilling can cause significant damage to electrical components that aren’t insulated against water damage.

Make sure that you take into account the number of bathers that are going to be in the hot tub at any one time as it will raise the water level significantly.

Never allow the water level to fall below the minimum fill line. If there isn’t enough water, the pump will be overworked, sucking in air.

Low water levels also mean that the water is not able to flow properly through the filters, causing damage to the spa and potential health risks to you through unsanitary water.

Maintaining the correct water levels is key to having your hot tub run efficiently and safely. Don’t forget that the water level will need to be topped up periodically to ensure it stays above the minimum fill line.

How often should I add water to my hot tub?

You will need to add fresh water to your hot tub every 1 – 2 weeks. Hot tubs lose water through evaporation and spillages as people exit the spa. If your hot tub is in constant use and doesn’t have a cover, you can expect to lose more water, requiring more frequent top-ups.

You need to test and balance the water each time you top up your spa with fresh water. I recommend using a water drop test kitOpens in a new tab. for the most precise results.

You can significantly reduce the amount of water that is lost by combining your insulated cover with a floating thermal blanketOpens in a new tab.. They prevent evaporation by up to 95% and are inexpensive.

Floating blankets also protect your main hot tub cover by creating a barrier that stops it from absorbing moisture, significantly prolonging its lifespan.

There are so many more advantages to owning one. Check out my article to read more on the benefits of using a floating blanket.

If your hot tub is losing significant amounts of water overnight, or the level drops by more than 2 inches (50mm) a week, then it’s likely that there is a leak somewhere.

Leaks must be repaired right away, ideally by a professionalOpens in a new tab.. Make sure to cut all power to the hot tub while trying to locate the source of the leak to avoid electrocution.

How long does it take to heat a hot tub after filling?

It takes between 5 – 9 hours to heat an average-sized hot tub to 104°F (40°C). Spas heat up at a rate of 6 – 11°F (3 – 6°C) per hour. The exact amount of time will depend on factors such as your spa’s capacity, heater size, insulation, air temperature, and location.

You can avoid the hassle of going back and forth into the yard by using a wireless floating thermometerOpens in a new tab.. It enables you to monitor the water’s temperature from the comfort of your home using an app on your smartphone.

More expensive hot tubs are equipped with heaters that are suitably matched to the spa’s water capacity, making them thermally efficient.

If your spa is a budget model, then you can expect a longer wait for the water to heat. The heater will also be under a lot more stress if it isn’t appropriately matched in size.

You can reduce heating times by ensuring that all the components inside the hot tub are in good working order. When the components are in good shape, the water is able to flow freely, increasing its thermal efficiency.

The condition of the filters plays a significant role in reducing heating times, so ensure that the filters are always kept clean and clear using filter cleanerOpens in a new tab..

If you can no longer get the filters clean using filter cleaner, then it’s time to replace them. Don’t think that you can save money using old filters as the increase in energy will outweigh the cost of new filters.

Combining your main cover with a floating blanket is yet another reason to buy one as it’ll significantly reduce the amount of time it takes to heat up.

Hot tubs lose a lot of heat through the base, so I recommend having it sit on these special foam matsOpens in a new tab. to keep it insulated. They even help to reduce the amount of noise your spa makes too.

When can I add chemicals to my hot tub after filling?

You should wait until the temperature of the water in your hot tub reaches 80°F (27°C) before adding sanitizing chemicals. This is because the heat helps to dissolve the chemicals more easily into the water.

It’s best to measure the chemicals before adding them to the spa to avoid waste, saving you money.

Never mix chemicals. Add the chemicals one by one, allowing them time to dissipate before adding the next.

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