Can You Change the Water in an Electric Hot Water Bag?

Yes — you can change the water in your electric hot water bag, and it takes less than 5 minutes.

All electric hot water bags sold in Bangladesh have a rubber-sealed refill point at the back of the bag. Every bag comes with a small plastic funnel in the box, specifically for this purpose. The water is not permanently sealed — it is designed to be changed for maintenance.

If the existing water in your bag has turned yellow, developed an unusual smell, or your bag is not heating as well as it used to — a water change will usually fix the problem. Here is how to do it.

Where Is the Refill Point?

Turn your bag over and look at the back surface. You will see a small circular rubber cap or plug — slightly raised, typically located near the centre or top of the back panel. This is the refill point.

The rubber cap creates a watertight seal that holds under the pressure of warm water during normal use. It is designed to be opened by hand — no tools required — when the bag is completely cool and unplugged.

If you have never opened it before, it may feel stiff. This is normal. Press down firmly on the centre of the cap and twist, or grip the edge and pull — it will come free. If it is your first time, it may require a little more force than expected.

When Should You Change the Water?

You do not need to change the water after every use. But there are clear signs that it is time:

Change the water immediately if:

• The water has turned yellow, brown, or cloudy
• You notice an unusual or musty smell when the bag heats up
• The bag takes noticeably longer to heat than it used to
• You can see visible discolouration, scale, or mineral deposits when you look inside

Change the water on a routine schedule:

How to Change the Water — Step by Step

What you need:

• Your electric hot water bag (cool and unplugged)
• The small plastic funnel from your bag’s box (or any household funnel)
• A sink or basin to drain the old water into
• Fresh tap water

1. Lay the bag on a flat surface or hold it over a sink. Make sure it is fully cool — you should be able to hold it comfortably with no warmth at all.
2. Locate the rubber refill cap at the back of the bag.
3. Open the cap by pressing the centre firmly and twisting, or gripping the edge and pulling. It should come out cleanly. Set it aside in a safe place — do not lose it.
4. Tip the bag gently to drain the old water completely into the sink. Give it a gentle squeeze to help the last of the water out.
5. Insert the small plastic funnel into the opening.
6. Pour fresh tap water slowly through the funnel. Fill to approximately 75% of the bag’s capacity — do not overfill. On BeGreat (1000ml) this is about 750ml. You will feel the bag become firm but still flexible when it is at the right level. If your bag has a fill line marked inside or on the label, use that as your guide.
7. Remove the funnel. Check the opening and the edge of the cap — make sure there is no water on the rubber seal that could prevent it from closing properly. Dry with a cloth if needed.
8. Push the rubber cap back into the opening firmly. Press it in and twist if it has a locking direction. Pull it gently from the outside to confirm it is seated securely — it should not come out with light pressure.
9. Dry the outside of the bag and the cap area thoroughly with a cloth.
10. Your bag is ready. Plug in and charge as you normally would — the fresh water will heat up exactly as before.

What Type of Water Should I Use?

• ✅ Fresh tap water is fine for all models — this is all you need
• ✅ Filtered or bottled water is a good option if your tap water is very hard (high mineral content), as it will reduce scale buildup inside the chamber over time
• ❌ Do not use boiling water — it is not necessary and expanding steam inside a sealed bag can cause pressure buildup
• ❌ Do not add salt, essential oils, fragrance, vinegar, or any other substance — plain water only
• ❌ Do not use water that has been sitting in a glass or jug for a long time — use fresh running tap water

How Much Water Should I Put In?

Fill to approximately 70–75% of the bag’s maximum capacity. This leaves room for the water to expand slightly as it heats, without creating excess pressure on the seal.

If you are unsure, fill until the bag feels firm but still flexible — not hard or taut. An overfilled bag puts stress on the rubber seal and the water chamber walls.

Frequently Asked Questions

Can I change the water if my bag is still under warranty?

Yes. Changing the water using the built-in refill point is normal maintenance and does not void the warranty. The refill cap exists specifically for this purpose. The warranty only becomes void if the bag is physically damaged, misused, or tampered with beyond the refill cap.

What if I cannot get the rubber cap back on securely?

First, make sure both the cap and the opening are completely dry — water on the rubber prevents a proper seal. Then try pressing the cap in with firm, even pressure while twisting slightly. If it still will not seal correctly, do not use the bag — contact hammad.biz for a replacement cap or a replacement bag. Using a bag with a loose refill cap risks leakage near the electrical components, which is dangerous.

Is it normal for the water to look slightly discoloured when I drain it?

Mild yellowing is normal after several months of use — this is mineral deposits from the water and harmless residue from the heating process. Dark brown, black, or foul-smelling water should be drained and the interior rinsed (pour fresh water in, shake gently, drain again) before refilling. If discolouration returns very quickly after a fresh fill, contact hammad.biz.

My bag did not come with a funnel. What do I do?

Any small household funnel will work — the opening is a standard size. You can also carefully pour from a small measuring jug or bottle with a narrow spout. Go slowly to avoid spilling water into the charging port area of the bag. If you need a replacement funnel, contact hammad.biz.

How do I know when to stop filling?

Stop filling when the bag feels firm but still flexible — you should be able to gently squeeze it and feel some give. If the bag feels hard or taut like a fully inflated balloon, you have overfilled it. Drain a little water until it has the right feel.

Keep Your Bag Working Longer

Changing the water regularly is the single most important maintenance step for your electric hot water bag. Fresh water heats more efficiently, keeps the heating element clean, and prevents the mineral buildup that shortens bag life.

For a complete guide on how the heating mechanism works and what each component does, see: How Electric Hot Water Bags Work

For step-by-step instructions on safe daily use and charging, see: How to Use an Electric Hot Water Bag Safely →

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