Dosing System Installation Method Statement: What to Include

A dosing system installation method statement tells the client and the supervising engineer how you will install the equipment, how long it will take, how you will keep people safe and how the result will be checked. Seven sections cover it: scope, preparation, work sequence, schedule, safety, quality control and commissioning. Most rejected documents are generic equipment method statements with a new title, and they miss what makes chemical dosing different: hazardous chemicals, flooded suction, the test medium and pump oil filling. This guide is for project engineers and site supervisors, using a skid-mounted dosing package as the example.

Structure of a dosing system installation method statement

A version that usually passes review looks like this:

Figure 1: LEWA ecoflow diaphragm metering pump. Image source: LEWA official website

1. Project scope
2. Preparation
3. Work sequence and methods
4. Schedule
5. Safety and environmental measures
6. Quality control
7. Commissioning and handover

Length matters less than clarity. Each section should say who does what, when, and to what standard. We have seen thick documents where nobody could find the hydrotest medium, and short ones signed off on first review because they addressed the actual equipment.

Project scope

State the purpose, the chemicals, the number of units, the location and the tie-in to the main process. Ammonia for boiler feedwater, scale inhibitor for cooling water and coagulant for wastewater each lead to very different safety sections later in the dosing system installation method statement.

Identify the equipment by type. A skid built around LEWA ecoflow diaphragm metering pumps, or a LEWA chemical injection package, will have its own requirements, such as whether the pumps need hydraulic oil before start-up. Distance from the skid to the injection point also matters; see where to locate a dosing skid.

Preparation

Technical preparation

Drawing review, the manufacturer's installation manual and a recorded toolbox briefing. Check every interface against the site: make-up water, discharge, overflow and drain line sizes and flange standards. Our guide to dosing system piping connections explains the four lines.

Site preparation for the dosing system installation method statement

Re-survey plinth dimensions, levels and embedded plates. Confirm the lifting route, temporary power, lighting and the eyewash station location. Inspect the skid on delivery, count accessories and leave protective caps on pump heads and valves until installation.

Work sequence in the dosing system installation method statement

This is the core of the document. Write it in real order:

1. Plinth acceptance and setting out
2. Lifting, positioning, leveling and anchoring the skid
3. Process piping: suction, discharge, overflow and drain
4. Accessories: relief valve, back pressure valve, dampener, injection quill
5. Electrical and instrument wiring, earthing
6. Pressure testing and flushing
7. Pump run test and integrated commissioning

Give the method for each step: the jointing method for plastic pipe, the welding method for stainless, clean water as the test medium and never chemical, and oil filling for hydraulic diaphragm pumps per the manual. For an integrated coagulant unit, see our PAC dosing system installation walkthrough.

Schedule

A bar chart or milestone list both work. Show dependencies: equipment delivery and plinth acceptance are the two start points, piping and wiring can overlap, and testing and flushing must finish before commissioning. Duration typically depends on the number of units, pipe run length and whether tie-ins need a process shutdown, so allow time to wait for that window.

Safety and environmental measures

This is where a dosing system installation method statement differs most from a general one.

Before tying into a live system, stop the pumps, release pressure, isolate, lock out and confirm the line is free of chemical before cutting or hot work.

Cover the lifting plan and exclusion zone, hot work permits, chemical PPE (goggles, chemical gloves, eyewash for acids, caustics and hypochlorite) and collection of flushing water so it does not go to storm drains.

Quality control and commissioning

List hold points: plinth level, skid leveling, pipe fall, flange bolt torque, weld appearance and earth resistance, each with a record sheet.

For commissioning, give steps and acceptance criteria: no leaks on water, correct motor rotation, relief valve set pressure verified, flow measured with a calibration column at real back pressure, and every interlock and alarm tested. Handover documents usually include installation, pressure test and commissioning records plus the manufacturer's manuals.

Why reviewers send it back

When a dosing system installation method statement comes back with comments, the reasons are usually the same few. The test medium is missing or says "as required". The chemical hazards are copied from a general template and do not name the actual chemicals. The tie-in to a running line has no isolation steps. The pump section ignores priming, so nobody planned for flooded suction or venting. Fix those four before you submit, and the second review is often a formality. If the client has its own template, keep their headings and slot your dosing system installation method statement content underneath rather than fighting the format.

Conclusion

A dosing system installation method statement does not need to be long. Build it on the seven sections and include the items unique to dosing: chemical hazards, shutdown tie-ins, test medium, pump oil filling and flooded suction. Compare equipment details in our dosing skid range and the LEWA brand page. Send us the chemicals, number of units, site conditions and schedule, and contact our engineers to check the equipment sections of your dosing system installation method statement.

FAQ

Does a dosing system installation method statement need an expert review?

Usually not. A standard dosing skid is not high-risk work, but heavy lifts or work at height may need a separate lifting plan under local rules.

Can we pressure test with the chemical?

No. Test with clean water, flush, then introduce chemical, so any leak during testing is harmless.

Should the document list pump models?

Yes, model and main data. Reviewers need to see that your sequence suits the equipment, for example whether oil filling is required.

How long does installation usually take?

It depends on unit count and tie-in access. Setting a single skid is quick; most time goes on pipework and waiting for shutdown windows.

Can the method statement and commissioning procedure be one document?

On small jobs, yes. On larger projects keep them separate, because the commissioning procedure has to describe every interlock and alarm test.