A shower that trickles or a tap that takes an age to fill a kettle is frustrating. Before you buy a pump or a new showerhead, it's worth working out what's actually wrong. Low pressure can come from your own pipes, the type of hot water system you have, or the supply in the street — and the fix is completely different for each.
Pressure or flow?
Plumbers talk about two things: pressure (how hard the water pushes) and flow (how much comes out). You can have decent pressure but poor flow if a pipe is narrow or partly blocked. A simple test: time how long it takes to fill a litre jug from the kitchen cold tap. Slow filling at every tap points to the supply or main pipework; slow filling at one tap points to that tap or its pipe.
Step 1: Is it one tap or all of them?
If it's just one tap or shower, the problem is almost certainly local: a clogged aerator or showerhead, a half-closed isolating valve, or a faulty tap cartridge.
If it's everywhere, check whether it's hot, cold or both. Weak hot water only often points to the hot water system — a gravity-fed cylinder, a combi boiler issue, or a blocked heat exchanger. Weak everything points to the supply.
Step 2: Clean aerators and showerheads
Unscrew the aerator on the end of the tap spout and the showerhead, and rinse out any grit or debris. Glasgow's water is famously soft, so limescale is less often the culprit here than in hard-water areas, but grit and debris from old pipework can still block the fine mesh — especially after work on the mains.
Step 3: Check the valves
Make sure your stopcock is fully open — it's surprisingly common for it to be left half-closed after a previous repair. Check the small isolating valves under sinks and on the pipes to the toilet and shower too.
Step 4: Ask the neighbours
If your neighbours have the same problem, it's probably the supply. Scottish Water publishes planned work and supply issues, and you can report low pressure to them. In tenements, the pressure on the top floor is often lower than on the ground floor, simply because the water has further to climb.
Common causes inside the home
Old pipework is a big one in older Southside properties. Narrow lead or corroded iron pipes restrict flow, and lead pipes should be replaced anyway for health reasons. A hidden leak can also drop pressure — if your water meter moves when every tap is off, or you hear water running when nothing's on, call us.
Gravity-fed systems — with a cold tank in the loft and a hot water cylinder — rely on the height of the tank for pressure, so showers on the floor just below the tank can be weak. A shower pump can help, but it must be fed from the tank, never connected directly to the mains, which the water regulations don't allow.
Combi boilers heat water on demand, and their flow rate is limited by the boiler's size. If two taps are on at once, both will slow down. That's a limitation of the system, not a fault — though a boiler that's getting slower over time may need a service from our Gas Safe registered partner engineer.
When to call a plumber
Call us if pressure drops suddenly, if the problem is throughout the house and your neighbours are fine, if you suspect a leak, or if you're planning a new shower and want to know what your system can handle. We'll test the pressure and flow, find the restriction and explain the options, from a simple valve fix to replacing old pipework.
Planning a new bathroom? Tell us about low pressure in the planner notes. Choosing the right shower for your system — mixer, electric or pumped — is one of the most important decisions in a bathroom renovation, and it's much easier to get right at the planning stage.