Why I Bought a Water Pump Twice

This story starts with a pump that was actually good. Phoenix came from the factory with a Lilie Soft — a diaphragm pump with 11.3 l/min flow rate, widely used in motorhomes. Excellent value for money. Quiet, reliable, trouble-free.

But it has one physical limitation that can't be eliminated — and that's what eventually led me to replace the pump. Not once, but twice.

Lilie Soft and That Characteristic Humming

Lilie Soft is a constant-flow pump — it always runs at full speed, regardless of how much water you're drawing. Open the tap fully and everything works fine. The problem comes when you open the tap just a little.

The pump keeps pushing full flow, but the water has nowhere to go. The result? Some water recirculates through the pump chambers, producing that characteristic humming or clicking sound every experienced motorhome owner recognises instantly. During the day it's no issue at all. But at night, when you quietly head to the toilet, that sound wakes up the whole van.

It's not a fault. It's physics. And with this type of pump, there's simply nothing you can do about it.

First Attempt — Carawater Intelligent SmartPump

The solution seemed obvious — switch to a variable-speed pump. I chose the Carawater Intelligent SmartPump ISP-12-4K-15. A four-chamber pump with up to 15 l/min flow, Bluetooth app control, and three selectable pressure modes: 1.4 / 1.8 / 2.2 bar.

On paper, Carawater really does look good. The pump adjusts its speed based on pipeline pressure — if pressure drops (tap opened), it speeds up; if pressure rises (tap closed), it slows down. In the first two modes (1.4 and 1.8 bar) the pump is reasonably quiet. The problem appears at 2.2 bar mode, specifically when you open the tap fully or take a shower — the noise there is noticeable. Most owners settle on 1.8 bar as a compromise, and in that mode Carawater is acceptably quiet. The price is also not much higher than Lilie Soft.

After installation it was clear the app worked, the pressure modes worked, the flow matched the specs. But on the one specific point I'd changed pumps for, the result wasn't what I expected. Carawater is better than Lilie Soft, yes — but I wanted the night-time noise problem to disappear completely. It didn't.

I'd solved everything except the one thing I actually wanted to solve.

Second Attempt — Lilie IQflow 12.3 (Not 11.1)

Eventually I went with Lilie IQflow 12.3. One important note first: Lilie makes two IQflow models — 11.1 and 12.3. The eleven is three-chamber, the twelve is four-chamber. For a motorhome with multiple simultaneous draw points — shower, kitchen, toilet — go with the 12.3. The real-world difference is significant. Don't accidentally buy the 11.1.

The difference from Carawater was immediately obvious. The pump is virtually inaudible — thanks to completely smooth operation, you simply can't hear it in the van. At all. Need water in the middle of the night? You won't hear the pump, and water flows just like at home.

Why IQflow Works Differently Than Carawater

The technological difference is fundamental. Lilie holds a patent on flow measurement — you won't find this approach anywhere else yet.

Carawater controls motor speed based on pipeline pressure. The cause of the noise is simple: in a higher pressure mode (2.2 bar) the motor spins faster — and a faster-spinning motor is louder. In lower modes (1.4 and 1.8 bar) the RPMs are lower, so the pump is quieter. That's why the 1.8 bar compromise works — it's not technical magic, just lower revs.

IQflow has a flow sensor that measures directly how much water is flowing. The pump always knows exactly how many RPMs it needs at any given moment — it never unnecessarily spins at full power, always precisely what the situation demands. The motor runs smoothly, without abrupt transitions. The IQflow is simply the Mercedes of motorhome pumps — the result: you just can't hear it in the van.

One Disadvantage: IQflow Needs Clean Water

IQflow has one specific requirement — it needs perfectly clean water. The flow sensor is precise, and contaminants will clog it. Before installation, replace the filter with a new one — it's included in the box, so you won't forget. But that alone isn't enough.

I'd recommend cleaning your water tanks before switching to IQflow. I found after years of operation — even though I thought the tanks were clean, since I use silver grids in them — that there was residue on the walls and sediment on the bottom. I'll cover how to clean water tanks and what products to use in a separate article.

In short: do a full water system clean-up before installing IQflow. It's worth it.

Was It Worth It?

Absolutely.

Tonight I can run the tap and hear nothing that disturbs the peace in the van. That was the whole point from the beginning.

The biggest lesson from this upgrade wasn't technical, though. It was that specifications on paper — flow rate, pressure, Bluetooth app — say nothing about how loud a pump will actually be at partial draw at 2am. That you can only verify by listening in your own vehicle.