SK-18AE Wall-Mounted Condensate Pump

What the SK-18AE is designed to do

Split air conditioners remove moisture from the room air as they cool. That water collects in the indoor unit's drip tray and has to leave the building. Where a gravity drain can fall continuously to an outside wall, gully or soil stack, no pump is needed. Where the drain would have to run uphill, travel a long way along a wall, or cross a ceiling void, a condensate pump collects the water and pushes it along a small-bore discharge pipe to a suitable outlet.

The SK-18AE is a mini pump intended for exactly that job on wall-mounted split units. It is small enough to sit neatly beside or below the indoor unit, and its sensor controls the pump so it only runs when water has collected. The result is a drain route that can follow the most practical path in the room rather than the one gravity would dictate.

It is aimed at the common domestic and light-commercial installation: a single wall-mounted indoor unit in a bedroom, office, garden room or server cupboard, rated up to 7.5 kW of cooling. For larger units, or where you want an audible overflow warning built into the pump itself, the SK-18CE corner pump is the alternative we stock.

Performance: flow, head and capacity explained

The flow rate of 18 litres per hour comfortably exceeds the condensate produced by a wall-mounted split unit of up to 7.5 kW in normal UK conditions. Actual condensate volume depends on room humidity, the set temperature and how long the unit runs, which is why pump makers quote a maximum cooling capacity rather than a single water figure.

The maximum head of 8 metres is the vertical height the pump can lift water with no horizontal pipe. In a real installation the pipe also runs sideways, and every metre of horizontal run, every bend and every narrowing reduces the effective lift. A widely used rule of thumb is to allow roughly one metre of lift for every ten metres of horizontal pipe. Plan with margin: a pump working well within its limits runs less often, more quietly and for longer.

Keep the first part of the discharge pipe rising vertically from the pump, then fall gently towards the outlet wherever possible. This lets the pump do its heavy lifting in the shortest distance and lets gravity help for the rest of the route, which reduces run time and noise.

Quiet enough for bedrooms and offices

The SK-18AE is rated at no more than 18 dB(A) at one metre. That is quieter than a whisper and, in most rooms, below the sound of the air conditioner's own indoor fan. Noise in practice depends on how the pump is mounted: fix it firmly, avoid it touching thin panels that can resonate, and make sure the discharge pipe is clipped so it cannot vibrate against a wall.

Because the pump only runs when the reservoir fills, it is silent for most of the time the air conditioner is operating. On humid days it will cycle more often, which is normal.

Installation overview

Mount the pump below the level of the indoor unit's drain outlet so condensate flows into it by gravity. Connect the indoor unit's drain hose to the pump inlet with a short, downward-sloping run with no dips where water could sit. Route the discharge pipe to an approved outlet, rising first and then falling, and secure it along its length.

Power should come from a suitable fused supply in line with current UK wiring regulations; electrical connections should be made by a competent person. Where the manufacturer's instructions provide a safety switch connection, wire it so the air conditioner stops cooling if the water level rises too high. This is the single most effective way to prevent a leak if the pump or its pipe ever blocks.

Once fitted, commission it: pour clean water slowly into the drip tray, watch the pump start and stop, and check every joint along the discharge route for leaks. Our installation guides walk through each step in more detail.

Looking after the pump

Condensate carries dust, skin cells and airborne particles washed off the indoor coil, and over time this can form slime in the tray, hose and pump reservoir. Clean the indoor unit filters regularly and inspect the pump every six to twelve months. Isolate the power, remove the reservoir cover as described in the instructions, rinse out any sludge and check the float or sensor moves freely.

If the pump runs constantly, never stops, starts making more noise than usual or water appears around the indoor unit, investigate straight away. Most faults turn out to be a blocked inlet, a kinked discharge pipe or a sensor fouled by debris rather than a failed motor.

SK-18AE or SK-18CE?

Choose the SK-18AE for a standard wall-mounted split system up to 7.5 kW where a compact pump fits beside the unit and a lift of up to 8 metres is ample. Choose the SK-18CE where the unit is up to 8 kW, you need up to 10 metres of head, a corner-shaped body fits the space better, or you want a built-in buzzer that sounds if the water level gets too high.

Delivery

Delivery is £8.99 to UK addresses. Order before 1pm on a working day and the pump is dispatched for next-working-day delivery; orders placed after 1pm, at weekends or on bank holidays leave on the next working day.

We sell single units to homeowners and installers alike. There is nothing to register and no account to create: add the pump to your basket and check out.

30-day returns

You have 30 days from the date of delivery to return a pump if you change your mind. The pump must be unused, in its original packaging and in a resalable condition. Return postage is paid by the buyer, and we recommend a tracked service, as the pump remains your responsibility until it reaches us. Once the returned pump has been received and checked, we refund the price of the pump; the original £8.99 delivery charge is not refunded. To start a return, email info@condensatepump.co.uk with your order details before sending anything back. This policy is in addition to your statutory rights, which are not affected.

2-year warranty

Every pump sold on CondensatePump.co.uk carries a 2-year warranty against manufacturing defects, starting on the date of delivery. Keep your order confirmation as proof of purchase. The warranty does not cover damage from incorrect wiring, blocked inlets caused by missing filtration, physical impact, or use with liquids other than air-conditioning condensate.

Frequently asked questions