Low water pressure in the shower: causes and fixes
If only the shower has low water pressure and the taps are fine, the cause is almost always in the shower itself: a shower head or hose blocked with limescale, a kinked hose, a clogged filter or failing cartridge in the mixer valve, or a partly closed isolation valve. If every tap is weak too, the problem is the supply to the house or the hot water system, not the shower. Start by unscrewing and descaling the shower head, which fixes a large share of cases in London's hard water. If the flow is still poor, or it dropped suddenly after work on the water main, the valve or the supply needs a plumber.
Loyal Plumbers · Updated
Discuss your plumbing workIs it just the shower, or the whole house?
This one question saves the most time. Run the cold kitchen tap, which is usually fed straight from the mains, then the bathroom basin taps on hot and cold. Compare them with the shower.
If the taps run well and only the shower is weak, carry on with this guide. If everything is weak, go to our main guide to low water pressure. Thames Water suggests checking that your inside stop valve, usually under the kitchen sink, is fully open, and asking neighbours whether they have the same problem, because a street-wide drop is the water company's to fix rather than yours.
| What you notice | Most likely cause |
|---|---|
| Shower weak, taps fine | Shower head, hose, mixer valve filters or cartridge, or a shower isolation valve |
| Shower weak on hot only, cold is fine | Hot supply restricted, a mixer cartridge fault, or the boiler or cylinder limiting flow |
| Shower drops when another tap or the washing machine runs | Pipework or supply that cannot feed two outlets at once |
| Electric shower weaker in winter | Normal for many electric showers: colder incoming water means a slower flow to reach the same temperature |
| Every tap and the shower suddenly weak | Stop valve not fully open, a leak, or a water company issue in the street |
| Weak ever since the shower was fitted | The shower does not suit the water system it is connected to |
Clean the shower head first
London has hard water, and limescale builds up in the small holes of a shower head until the spray turns into a few thin jets. Unscrew the head from the hose or arm, soak it for a few hours in a descaling solution or white vinegar, then rub the nozzles with an old toothbrush. Many heads have soft rubber nozzles you can flex to push scale out.
While the head is off, turn the shower on briefly. If the flow from the bare hose is strong, the head was the problem. If it is still weak, the restriction is further back.
Check the hose, flow restrictor and isolation valve
Look along the shower hose for kinks, especially where it hangs over the riser rail or drops into the tray. The inner lining of an older hose can collapse without any sign on the outside, and replacing it is cheap. Some shower heads and hoses also contain a flow restrictor, a small plastic insert fitted to save water. On a low-pressure system, that can leave you with very little flow.
Many showers have an isolation valve on the supply pipe, often a small screw-slot valve behind a panel, in the airing cupboard or near the shower. If someone has worked on the shower recently, it may have been left partly closed. The slot should line up with the pipe when it is fully open.
Mixer valve filters and cartridges
Thermostatic mixer showers have fine filters where the hot and cold supplies enter the valve, and a cartridge inside that blends the two. After work on the water main, or on an older system, grit and scale collect in those filters and cut the flow. A worn or scaled cartridge can also restrict flow, or cause the temperature to swing.
Cleaning the filters or replacing a cartridge usually means isolating the supply and taking the valve apart, and on a concealed valve it may mean working through an access panel. It is a routine repair for a plumber. Our guide to thermostatic shower temperature problems covers the cartridge faults in more detail.
When the shower does not suit the water system
If the shower has been weak since the day it was fitted, the problem may be a mismatch. In a house with a cold water tank in the loft and a hot water cylinder, the pressure depends on how high the tank is above the shower. A shower head on the top floor can have very little pressure, and some modern mixers need more than that system can give.
With a combi boiler, the shower's hot flow is limited by how much water the boiler can heat at once and by the mains pressure. Mixers also work best when the hot and cold supplies are at similar pressures; a mains cold and a tank-fed hot often fight each other. The fixes range from a different shower valve to a pump on a gravity system. A standard shower pump is not for a mains-fed or combi system, and pumping directly from the mains needs the water company's say first, as our guide to mains booster pump notification explains. Our guides to shower pump suitability and choosing a mixer or electric shower cover the options.
Electric showers with low flow
An electric shower heats cold mains water as it passes through. It has a fixed power, so when the incoming water is colder in winter, it slows the flow to reach the same temperature. Some drop in winter is normal. A sudden drop, a shower that cuts out, or one that will only run cold is not. Scale inside the unit, a failing solenoid valve or a pressure problem can all be to blame. Our guide to an electric shower that keeps cutting out covers those faults.
Do not open an electric shower unit yourself. Switch it off at its isolator and have it checked by a qualified person.
Getting the shower pressure sorted
Call a plumber if cleaning the head and checking the hose have not helped, if the pressure dropped suddenly, if the temperature is also unstable, or if you suspect a leak because the water meter keeps moving with everything off.
Loyal Plumbers has 10 vans covering London and everywhere inside the M25, 24 hours a day. When you get in touch, tell us whether it is only the shower or the whole house, whether it affects hot, cold or both, what type of shower it is, whether you have a combi boiler or a cylinder, and whether it has always been weak or has just changed. Our call-out charge is £60, and the plumber explains what they have found and what the repair involves before starting.
Common questions
- Why is my shower pressure low but my taps are fine?
- The restriction is in the shower: usually a scaled shower head, a kinked or collapsed hose, blocked filters in the mixer valve, a worn cartridge or a partly closed isolation valve.
- How do I increase water pressure in my shower?
- Descale the shower head, check the hose and remove any flow restrictor. If it is still weak, a plumber can clean the valve filters, replace a cartridge or check the system suits the shower.
- Why has my shower pressure suddenly dropped?
- A sudden drop often follows work on the water main, when debris blocks the valve filters. Also check that the stop valve and any shower isolation valve are fully open.
- Can I fit a shower pump to improve pressure?
- A standard shower pump suits a gravity-fed system with a cold water tank and cylinder. It is not for a combi, and pumping from the mains needs the water company's agreement first.
- Why is my electric shower weaker in winter?
- The incoming water is colder, so the shower slows the flow to heat it to the same temperature. Some drop is normal; a sudden change is not.
Sources and further reading
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