Low water pressure and poor shower pressure in Christchurch

First, which pressure is actually low?

It matters, because it points at completely different fixes. Run the cold tap in the bathroom, then the hot, and compare.

• Hot is weak, cold is fine. Much the most common in Christchurch, and it almost always means a low pressure hot water cylinder — the vented type with a header tank, standard in bungalows and older housing right through St Martins, Opawa, Beckenham, Spreydon and Cashmere. The hot side runs on gravity, so it is only ever as strong as the height of the tank above the shower.
• Both are weak. That is the supply into the house rather than the hot water. Usually the water main — corroded galvanised closing over from the inside, early alkathene, or a main that is simply too small for the house. Sometimes a partly closed toby or a failing pressure-limiting valve, which is a much cheaper answer.
• It drops when someone else runs a tap. Undersized pipework, or too many fixtures sharing one run.
• Only one outlet is weak. A blocked aerator or cartridge in that tap, and often a five-minute fix.

We check this before recommending anything. Fitting a pump to solve a problem that was a $40 valve is an expensive way to get there, and we would rather tell you.

The three real fixes

1. A booster pump

A shower or pressure pump sits on the low pressure system and lifts the flow to the shower and taps. It is the least disruptive of the three: no new cylinder, no re-piping, usually done in a few hours.

• What it suits. A sound low pressure cylinder with plenty of life left, where the only real complaint is the shower. Common in a house where the cylinder was replaced recently and nobody wants to spend again.
• What it does not fix. A pump boosts what is already there. If the cylinder is at the end of its life, or the cold side is weak too, a pump treats the symptom.
• Siting. Pumps make noise, so where it goes matters — under the house or in the cylinder cupboard, not against a bedroom wall. We will talk through that before installing rather than after.
• Twin or single. A twin-impeller pump boosts hot and cold together, which keeps a mixer balanced. A single boosts the hot only, which is cheaper but can leave a shower harder to set.

2. Low pressure to mains pressure upgrade

Replacing a low pressure cylinder with a mains pressure one puts the hot side at the same pressure as the cold. It is the fix that makes the most difference to how a shower actually feels, and it is what most people are describing when they say they want "proper pressure".

• What is involved. A mains pressure cylinder, a new valve set — pressure reducing, expansion control and a tempering valve on the outlet — and the header tank decommissioned.
• What gets checked first. The existing pipework has to be able to take mains pressure. Old galvanised, or undersized runs, may need replacing as part of the job, and we tell you that before we start rather than halfway through.
• And the main itself. A mains pressure cylinder can only deliver what the incoming main gives it. If the main is corroded or undersized, that gets sorted first or the upgrade disappoints — see watermains and supply lines.
• Timing. Usually the right moment is when the cylinder is due anyway. Replacing a sound low pressure cylinder purely for pressure is a real option, but we will be straight with you about the cost against a pump.

3. Gas continuous flow conversion

Converting to gas continuous flow removes the cylinder altogether. The unit heats water as it passes through and delivers it at mains pressure, so the pressure problem goes away with the cylinder, and so does running out of hot water.

• What it suits. Houses with gas already, or where bottled LPG is practical. Also households that keep running out — a continuous flow unit does not have a tank to empty.
• What is involved. The unit mounted on an exterior wall, gas run and sized, flue and condensate handled, water reticulated to it, and the whole installation certified on completion by a certifying gasfitter. We issue the gas certificate.
• The honest trade-off. Bottled LPG costs more per unit of energy than electricity does for a cylinder, so running costs depend on how much hot water you use and whether natural gas is available at the property. We will give you the real comparison rather than the sales version.

Gas hot water conversion is the work we get called for most. There is more on it on the certifying gasfitter page, including photos of recent conversions.

Which one is right?

Roughly: if the cylinder is sound and it is only the shower that bothers you, a pump. If the cylinder is due for replacement anyway, a mains pressure upgrade. If you have gas, or keep running out of hot water, a continuous flow conversion. And if the cold side is weak too, none of the three is the answer until the main is sorted.

We will look at what you have, check the pressure and flow at the fixtures rather than going off the description, and tell you what each option would cost on your house.