Weak hot water pressure is a common complaint in older houses, homes fed from a header tank, and anywhere the hot water system sits low and the bathroom sits high. A small in-line booster pump on the hot line can fix it. But before fitting one, it's worth checking it's the right fix, because boosting only the hot side can create a new problem at the mixer.
The Hyjet HBD15-90B
Per the listing, the Hyjet HBD15-90B ($518.05) is an in-line booster pump that lifts pressure in domestic hot water systems at showers, taps and appliances, for renovations and new builds. It has:
- A 120W, 240V single phase motor.
- A bronze (DR) body, rated to 95°C and 6 bar maximum operating pressure.
- Manual, auto and off modes. In auto, it starts when flow goes above 2.0 L/min.
- Barrel unions on suction and delivery, a built-in non-return valve, and horizontal or vertical mounting.
When a booster is the right fix
- Gravity-fed or low pressure hot water, such as a header tank or a low pressure storage heater, where the pressure is low by design.
- Height difference, where the hot water system is low and the outlets are well above it.
When it isn't
- Blocked or restricted pipework. Old galvanised pipe, a partly closed valve, a blocked shower head or a failing tempering valve cause low flow that a pump won't cure. Check these first.
- A pressure limiting valve set too low. If the heater's inlet has a pressure limiting valve, check its setting against the heater maker's maximum before adding a pump.
- Low pressure on both hot and cold. If the whole house is weak, the fix is on the supply side, such as a whole-house pressure pump, not a hot water booster.
Watch the cold side
A mixer tap or shower mixer blends hot and cold. If you boost only the hot, the hot side can end up at a much higher pressure than the cold. Mixers work best with balanced pressures, so an unbalanced supply can make the temperature hard to set and prone to swings, and can push hot water back into the cold line through a mixer. Check that your mixers and tempering valve suit the pressures you'll end up with, and that non-return protection is in place. A plumber can tell you whether the cold side also needs attention.
Installation
- Water authority approval. The listing notes that approval from the local water authority must be obtained before connecting directly to the water main.
- Stay within ratings. Keep the boosted pressure within the pump's 6 bar rating, the hot water heater's limits and AS/NZS 3500.4's limits for heated water services.
- Licensed trades. Plumbing connection by a licensed plumber; a weatherproof outlet or hard-wiring by a licensed electrician.
If the problem is waiting for hot water to arrive, not weak pressure, see our guide to hot water circulation pumps. The HBD15-90B is in the Hot Water Booster Pumps collection and available to order on backorder; contact PSA to confirm lead time.
Frequently Asked Questions
Will a hot water booster pump fix low shower pressure?
If the hot water pressure is low by design, such as gravity-fed or a low hot water system, yes. If the pipework is blocked or both hot and cold are weak, the fix is elsewhere.
Does boosting hot water affect the cold?
It can unbalance the pressures at mixers, making the temperature hard to set. Check your mixers and tempering valve suit the boosted pressure.
When does the Hyjet HBD15-90B turn on?
In auto mode, when flow goes above 2.0 L/min. It also has manual and off modes.
Do I need approval to install a booster pump?
Approval from the local water authority is needed before connecting directly to the water main, and installation should be done by a licensed plumber.