When comparing reverse osmosis proposals, first ask what the recovery percentage divides, under which operating conditions it was measured, and where the concentrate goes. Percentages based on different system boundaries cannot be compared directly.
Limits of supplier design references
DuPont’s February 2026 design guidelines for 8-inch FilmTec elements distinguish feedwater types and consider limits including permeate flux, element recovery and concentrate flow. They are not a universal parameter table for every membrane size, brand or water source.
What to check in a quotation
| Question | Evidence to obtain | Purpose |
|---|---|---|
| System boundary | Whether pretreatment, second-pass RO, recycle and storage are included | Avoid mixing percentages for different process boundaries |
| Design conditions | Water analysis, temperature range, hourly demand and design notes | Identify the feedwater and duty covered by the quotation |
| Water balance | Feed, useful permeate, concentrate and flushing records for the same period | Identify unmetered bypasses or non-production water use |
| Concentrate handling | Receiving point, permitted uses and applicable project requirements | Do not assume untested concentrate is suitable for irrigation |
| Long-term expenditure | Cost boundaries for electricity, chemicals, consumables, cleaning, servicing and disposal | Compare total costs for the same operating duty |
An example without invented figures
If one quotation gives equipment permeate flow and another gives useful water delivered to the point of use, clarify storage, flushing and operating hours before comparing them. A cost estimate should state its inputs, the date of unit prices and exclusions. It must not be presented as guaranteed savings.
Frequently asked questions
Is a higher recovery always a better purchase? Consider the actual feedwater, element limits, operation and maintenance requirements; one percentage cannot rank proposals by itself.
Can concentrate be used in agriculture? Check its analysis, intended use and applicable requirements first. Its origin in an RO system does not establish its safety or suitability for a crop.
References and scope
References checked on 9 October 2026. These are public reference materials. Gudian prepared the information checklists for project enquiries. A supplier manual does not establish a brand authorization for this website, and a paper does not show that Gudian equipment has achieved its research results.
- DuPont 8-inch FilmTec membrane system design guidelines; Rev. 14, February 2026. For the specified 8-inch FilmTec elements; not universal parameters for all brands, sizes or feedwaters.
Further preparation
- Quotation comparison and acceptance criteria
- Operating-cost information
- Water-treatment selection guide
Equipment and consumable requirements can first be discussed remotely. Supply, installation and site visits are confirmed for each project. Send only the equipment and water-quality information needed for the enquiry, and conceal personal contact details and sensitive third-party information in photographs.