Why ChengrongEra Don’t Recommend Raw Water Backwashing for Whole-House Ultrafiltration Water Filtration Systems

I recently received an inquiry from a prospective client who found us online.

He lives in a self-built rural house and uses municipal tap water, with no household water tower installed. He wants to install an ultrafiltration water filter on the main water inlet pipe for whole-house water filtration, instead of an under-sink water purifier that only treats water for a single faucet.

I’ve noticed that even though municipal tap water is much cleaner than natural well water, however, as residential buildings age, water pipes deteriorate and inner pipe walls accumulate more and more contaminants, more and more urban customers are choosing ultrafiltration water filters for whole-house water filtration.

Cuz ultrafiltration filtes could provide the highest filtration precision among all types of whole house water filtration systems.

Generally, the higher the filtration precision, the greater the flow resistance. However, as long as an ultrafiltration cartridge with the appropriate water flux is selected, the UF water filter will not compromise household water pressure or flow rate at all.

What makes this client’s situation tricky is that there is no public plumbing shaft in his residential building, leaving very limited space for installing a whole-house water filter. So he asked whether such a single UF water filter unit supports backwashing.

Worried I might not understand, he thoughtfully sent me a schematic diagram showing backwashing for a single ultrafiltration water filter. The image was a screenshot from the internet with another peer's watermark, so I won’t post it out. The backwashing solution shown in the diagram uses untreated raw water through a bypass pipe to back-flush the ultrafiltration membrane filter cartridge. From a professional perspective, however, I do not recommend that ChengrongEra customers use raw water for backwashing.

First, we need to clarify what backwashing means: it reverses water flow by 180 degrees, turning the original purified water outlet into the inlet.

Under normal operation, water flows from the surface of the outside-in microfiltration membrane into the membrane filaments. The PVDF outside-in membrane has evenly distributed filtration pores of 0.1μm, Impurities in the water such as sediment, rust, colloids, and insect eggs are larger than 0.1 microns, so they cannot pass through the pores with water flow, and instead attach to the surface of the PVDF membranes.

This is why the outer surface of the microfiltration membranes becomes very dirty, while the inside remains clean. It is also the reason that why turbid rural well water, spring water, muddy water, and municipal tap water become clear and transparent after filtration by PVDF outside-in membranes.

Simply put, it is due to high filtration precision.

When raw water is used for backwashing: water seeps from the inside of the membrane filaments outward. During this process, filtration will also occurs.

However, sediment, rust, and other impurities in the raw water will attach to the inner wall of the membrane filaments, causing secondary contamination of the filter cartridge and worsening clogging of the membrane pores. As the outside-in membrane, also known as a PVDF reinforced membrane, unlike its smooth outer surface, its inner wall is a rough inner lining that easily traps dirt and is difficult to clean thoroughly. Frequent backwashing with raw water will lead to increasingly severe membrane fouling.

That is why I always say: if you cannot use purified water for backwashing, it is better not to backwash at all.

For customers without a household water tower installeda, I generally recommend installing a small parallel ultrafiltration water filter next to the whole-house ultrafiltration system. The clean water produced by this small unit is then used to backwash the main whole-house ultrafiltration system.

Why is the ChengrongEra third‑generation export‑oriented rural whole‑house ultrafiltration filter designed with a double‑clamp structure? Only this structure allows users to easily perform backwashing and manual cleaning simultaneously. A single‑clamp structure, even if it supports clean water backwashing, cannot enable simultaneous backwashing and manual scrubbing of the filter cartridge. This is the only effective way to thoroughly clean the surface and filtration pores of PVDF membranes.

Since this customer does not have enough space to install two parallel ultrafiltration units for combined backwashing and scrubbing, for an outside-in membrane system, he can only rely on manual cleaning to slow down the decline in water flow. I suggested that he wait a while longer. ChengrongEra will soon launch a tool-free disassembly ultrafiltration water filter, which will be much more convenient for customers unable to perform backwashing.

ChengrongEra focuses on premium products only; we do not act as a general store. Every ultrafiltration system we launch is built to perform in the TOP 1% of the industry in quality, function and structure. So the new tool-free model still needs thorough testing before official release.

Luckily, the customer said his full house renovation won’t happen for several more months, so he was willing to wait.

In an era when trust is more precious than gold, having customers who believe in ChengrongEra this much — what excuse do I have not to make our ultrafiltration water filters the very best I possibly can?

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Based in Shenzhen, Chengrong Factory is a leading manufacturer in China with 19 years of expertise in ultrafiltration water treatment systems, ranking among the top 3 in the industry. We boast a full supply chain integration that is rarely found worldwide, and serve as a trusted ODM/OEM partner for multiple global first-tier brands. Chengrong Ultrafiltration Factory helps every customer operate with confidence and complete peace of mind.

In mid-2025, we launched our own factory brand — ChengrongEra. It ranks among the top 1% in the industry in manufacturing quality, product performance and structural design, with quality on par with world-leading global brands. Try a small order— you won’t go broke, I won’t get rich.

PS: You may not understand the Chinese in the video, but you can clearly see how our dual parallel setup allows two ultrafiltration filters to backwash each other.

This video also explains what I mean by hand-washing the PVDF membranes like scrubbing laundry while backwashing the filter cartridge at the same time.

【84】Unlike 99% competitors in the market, ChengrongEra whole-house ultrafiltration water filter uses filtered clean water for backwashing instead of raw water