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Description
If all the hot outlets served by your cylinder feel weak — upstairs and down, every tap and shower — then the SP21S is likely the best pump for you.
When the whole house runs weak, the problem isn’t one pipe; it’s the pressure feeding the whole cylinder. A single pump on a single branch can rescue one shower, but it can’t lift the whole house.
Whilst you may have been told a unvented sealed system can’t be boosted at all, the Shower Power Booster is the only pump designed specifically to work with unvented systems — and the right pair in the right places lifts everything.
The SP21S for unvented systems is two WRAS-approved booster pumps working as one. The most effective arrangement for whole-house hot water is one pump either side of the cylinder — one on the cold feed going in, one on the hot coming out — which double boosts the hot supply to every outlet. Alternatively, fitted to the incoming supply, the pair boosts all hot and cold outlets equally.
Both pumps start automatically when water flows — no switches, nothing to turn on — and share one 3-amp transformer.
Q: How does “one pump either side” work? A: One pump boosts the cold going into the cylinder, the other boosts the hot leaving it. Together they double boost the hot side — the one customers feel most.
Q: Would the SP22S be better for my house? A: The SP22S protects the hot and cold feeds to your outlets — best when showers fade as taps and toilets are used. The SP21S lifts the whole hot water supply — best when everything runs weak all the time.
Q: Is this safe with the cylinder’s pressure controls? A: Yes — the pumps are WRAS approved and designed for unvented systems. If you’d like reassurance on your exact setup, call 01928 620 099 before you buy.
[INSTALLATION] Link to installation and insert photo of where on the system to install.
Fit before or after the cylinder. A common and effective method is one pump on each side of the cylinder. Unsure how to position the pumps for your setup? Call the SPB helpline on 01928 620 099 and we’ll guide you.