How to Clean a Geyser Inlet Filter

Here is a scene I meet again and again. A family calls saying their geyser has “gone weak”, the hot water barely trickles from the tap, and they are convinced the heater is dying. Nine times out of ten I clear a clogged inlet filter, and the flow comes roaring back. It is one of the cheapest, most satisfying fixes in geyser care, and you can do it yourself. This is part of routine water heater maintenance that most people never hear about.

Let me show you what this little strainer is, why it clogs, and exactly how to clean it without any special skill.

What the Inlet Filter Is and Why It Clogs

Most storage geysers have a small mesh filter, a strainer, tucked into the cold water inlet connection. Its job is to stop grit, sand, rust flakes and loose scale from washing into the tank and the valves.

That is a useful job, but the mesh slowly catches everything the water carries. In many Indian homes the water is far from clean at the tap: borewell supplies bring fine sand, old GI pipes shed rust, and hard water leaves scale flakes. Over months, that debris builds into a mat across the mesh.

As the mesh blocks, less water gets into the tank, so less hot water comes out. The heater is fine. Its throat is just choked.

Signs your inlet filter needs cleaning

• Hot water flow has dropped while cold water flow elsewhere is normal.
• The geyser takes much longer to deliver hot water at the tap.
• You hear the tank refilling slowly or with a thin hiss after use.
• The problem grew gradually over weeks, not overnight.

If cold water pressure across the house is also low, the issue is upstream, not your filter. But if only the hot side has weakened, the inlet strainer is the first thing I check.

What You Will Need

This is a light-tools job. You almost certainly have everything at home already.

Item	Why
Adjustable spanner or pipe wrench	To loosen the inlet connection nut
Bucket and old cloth	To catch the water that will drip out
Old toothbrush	To scrub the mesh clean
PTFE (Teflon) tape	To reseal threads on refit
Torch	To see into the inlet clearly

Have a small container handy too. The mesh strainer is a little part, and it loves to roll away down a bathroom drain the moment you set it down.

Cleaning the Filter Step by Step

Work slowly and keep track of the small parts. Here is the sequence I follow on every service.

1. Switch off the geyser at the MCB and let the water inside cool for a while.
2. Close the isolation valve on the cold inlet, or shut the main supply if there is no isolation valve.
3. Open a hot tap briefly to drop the pressure in the line.
4. Place your bucket and cloth under the inlet, then loosen the inlet connection nut with the spanner.
5. Ease the fitting apart and find the small mesh strainer inside the inlet port or the nut.
6. Lift the mesh out carefully and look at it against the light. A clogged one looks grey and matted.
7. Rinse it under a running tap and scrub gently with the old toothbrush until the mesh is bright and open.
8. Refit the clean strainer the same way it came out, rewrap the threads with fresh PTFE tape, and tighten the joint firmly.

Once it is back together, open the isolation valve, let the tank refill fully, and check the joint for any drip under pressure. Only when a steady, air-free stream runs and there is no leak do you switch the power back on.

If Cleaning the Filter Does Not Fix It

Sometimes the strainer is spotless, or you clean it and the flow is still weak. Then the blockage is deeper, and the usual culprit is scale.

In hard-water homes, calcium and magnesium build up as a hard crust inside the tank, on the element, and around the outlet. That narrows the passages the same way the mesh did, only inside where you cannot reach with a toothbrush.

• If flow is weak and heating is also slow, suspect scale on the element and in the tank.
• If you see white flakes coming out when you open the inlet, that is scale breaking loose.
• If the water was fine last winter and has slowly worsened over a year, scale fits the pattern.

That is when a proper tank flush or descale is due. Our guide to flushing a water heater clears loose sediment, and a full geyser descaling tackles the hard crust on the element and tank walls. Cleaning the inlet filter is the quick first step; these are the deeper service.

How Often to Check It

Frequency depends entirely on your water. Clean supply on newer pipes stays clear for a long time. Sandy borewell water or old galvanised pipes clog a strainer fast.

Your water supply	Suggested check
Clean municipal, newer pipes	Once a year
Hard water, city supply	Every six months
Borewell or sandy water	Every three months
After any pipeline work nearby	Check soon after

That last row matters more than people expect. Whenever the local body digs up a road or the building does plumbing work, a rush of loosened grit and rust hits every filter downstream. I get a wave of “weak geyser” calls a week after any pipeline repair on a street.

A Few Habits That Keep the Filter Happy

Small habits stretch the time between clean-ups and protect the whole geyser, not just the strainer.

• Fit a whole-house or line sediment filter if your supply is gritty, so debris is caught before it ever reaches the geyser.
• Flush the tank on schedule so loose scale does not migrate to the inlet and outlet.
• Keep a spare mesh strainer of the right size, since old ones can tear when you clean them.
• Note the date each time you clean it, so you learn your home’s real interval.

Hard water is behind most of this, and it is worth understanding the chemistry once. You can read a plain background on hard water to see why scale forms and why a filter and regular flushing matter so much in much of India.

Frequently Asked Questions

Where is the inlet filter on a geyser?

It is a small mesh strainer sitting inside the cold water inlet connection, the blue side where the mains pipe enters the tank. Depending on the model, it sits in the inlet port itself or inside the connecting nut. Shut the water and power off, loosen that inlet joint, and you will find it.

Why has my geyser hot water flow suddenly dropped?

A clogged inlet filter is the most common cause when only the hot side weakens while cold water elsewhere is normal. Grit, sand and scale flakes mat across the mesh and choke the flow into the tank. Clean the strainer first. If flow stays weak, suspect scale deeper in the tank.

How often should I clean the geyser inlet filter?

It depends on your water. Clean municipal supply on newer pipes may need it just once a year. Hard water calls for every six months, and sandy borewell water every three months. Always check within a week or two of any pipeline repair nearby, which sends a rush of grit downstream.

Can I clean the filter without a plumber?

Yes. It is a simple 15-minute job with an adjustable spanner, a bucket and an old toothbrush. Switch off the power at the MCB, shut the water, loosen the inlet joint, rinse the mesh clean, reseal with PTFE tape and refit. Only call a plumber if the joint is seized or you cannot reach it.

What if the mesh strainer is torn or missing?

Replace it with a matching one from a hardware shop or the geyser brand. Running without the strainer lets grit and scale wash straight into the tank and valves, which causes bigger problems later. It is a cheap part, so keep a spare of the right size, since old mesh can tear during cleaning.

A Small Clean With a Big Payoff

The inlet filter is a tiny part that quietly decides how well your geyser delivers. When the hot water weakens, reach for a spanner and a toothbrush before you reach for your wallet. Power off, water off, rinse the mesh, reseal and refit, and most weak-flow complaints simply vanish.

Make it a habit alongside your other checks, and if the flow stays poor, move on to a flush or descale. For the full seasonal routine, see our water heater maintenance guide, or browse all our maintenance guides to keep your geyser running strong for years.