What chimney size do I need: diameter 1000 vs. 1300 vs. 1600 mm

What shaft size do I need: diameter 1000 vs. 1300 vs. 1600 mm

When a customer comes for a shaft, most of them know only one thing: they need a shaft. But what diameter? What depth? How much space does it actually take up in the ground? Most people stop here and wait for advice. And this choice will decide whether maintenance and service will be comfortable, or whether you will twist like a snake in a narrow opening at every inspection. The correct shaft size is not just a technical formality – it is a practical matter that will accompany you for decades.

This article will cover the topic from the basics. We will look at what the individual dimensions mean in practice, when to use the compact diameter of 1000 mm, when the medium diameter of 1300 mm is a reasonable choice, and when it is worth going for the large diameter of 1600 mm. We will explain how the depth of the shaft, the type of fittings, the access for the service technician, the ground conditions, and many other factors that you won't find in a catalog but will run into at every step, come into play.

What exactly does the "diameter" of a shaft indicate and why every centimeter matters

When a manufacturer refers to a diameter of 1000, 1300 or 1600 mm, it always refers to the external diameter of the shaft body – that is, the outer dimension of the plastic cylinder. The usable internal diameter is smaller by the thickness of the shaft wall. For example, in standard polypropylene shafts, the wall thickness is usually 15–25 mm, so the actual internal diameter is 3–5 cm smaller than the stated external dimension.

This directly affects two things: how much space you have inside for fittings and for your own body during a service intervention. This is the point where customers most often underestimate the choice. The difference between a shaft with an internal diameter of ~950 mm and a shaft with an internal diameter of ~1550 mm is huge – we are talking about a difference in usable floor area of about 0.71 m² compared to about 1.89 m². That is almost three times as much!

This means in practice: in a small diameter of 1000 mm, the technician can only work if he avoids entering the shaft – that is, he has to work from above, with tools lowered down. If you need to replace a ball valve, tighten a coupling or check a submersible pump, this is done with great limitations in a 1000 mm shaft. In a 1300 mm shaft, you can get to the bottom and work with some limitations (narrow stance, no significant movement), while in a 1600 mm shaft, you can move comfortably, access the fittings from the sides and even install a larger electrical fitting.

Diameter 1000 mm: for which situations is it actually sufficient

A shaft with an external diameter of 1000 mm is the smallest commonly available size for underground shafts intended for water metering or inspection purposes. In practice, it is suitable where space is limited and the volume of fittings is minimal. Let's break it down in detail.

Water metering shaft with a simple meter and direct access

If you have a family house connected to the public water supply, the water metering assembly consists of: a closing valve before the meter, the meter itself, a check valve and another closing valve after the meter. This simple linear assembly on a DN 32 or DN 40 pipe takes up about 40–60 cm horizontally and does not need more than 20–25 cm of mounting height. Such an assembly fits into a 1000 mm diameter shaft with sufficient reserve for pipe insulation and sealing elements. Technical standards EN 805 and STN 75 5401 define the minimum free space around the measuring assembly – and for a simple direct meter DN 32/40, a 1000 mm shaft is standardly sufficient.

Where it stops working: if you have a DN 50 or larger pipe, if you have two branches (e.g. garden + house), if a filter is needed before the meter or a pressure stabilizer, the 1000 mm diameter shaft becomes critically small. Pressure reducing valves, Y-filters and multiple valves are components that require significantly more space.

Inspection shafts for sewage

In the sewage world, a diameter of 1000 mm is commonly used for inspection shafts on sewage lines, where it is not necessary to physically enter during normal operation. These are shafts where the technician checks the flow condition with a camera from above, or flushes the pipe, but does not need to physically enter the shaft and turn around. The bottom of the inspection shaft is simple in such a case – either flat with a flow channel (so-called kinta), or with a branch. An example is a shaft bottom with a backflow valve 400/160 – it is a simple functional element that performs its function without the need for a large space around it.

Diameter 1300 mm: the golden middle path for most home installations

A diameter of 1300 mm is in practice the most sold size for family homes and smaller businesses, and for a good reason. It provides enough space for standard water metering assemblies, simple pumping installations and service accessibility – and is reasonably compact for excavation.

What Actually Fits into a Shaft with a Diameter of 1300 mm

Practical experience from hundreds of installations shows that a shaft with a diameter of 1300 mm comfortably accommodates:

• A complete water metering assembly on a DN 32–63 pipe, including a Y-filter, water meter, check valve, and two shut-off valves
• A pressure-reducing valve (PRV) if required after the water meter
• Pressure gauges and sampling valves
• Cable supply and an electrical socket for a possible pump
• Thermal insulation (e.g., polystyrene half-shells) around the entire assembly
• Sufficient space for maintenance work from the top without the need to enter the shaft

An important aspect is that the excavation for a 1300 mm shaft is significantly less expensive than for a 1600 mm shaft. Excavation companies typically charge by the cubic meter of soil removed, and increasing the outer diameter from 1300 to 1600 mm means an additional approximately 0.5 m³ of soil and the same volume of backfill material at a depth of 1 meter. At depths of 1.5–2 meters, the differences become even more pronounced.

A typical example for a 1300 mm shaft is the circular PP water metering shaft 1300×1000 self-supporting plastic. Its construction from polypropylene plastic is designed to withstand lateral soil pressure without the need to concrete the wall – self-supporting is a key parameter, which we discuss in more detail in the article Plastic shaft vs. concrete shaft: which is more cost-effective?

When 1300 mm is on the Edge – Warning Signs

A few situations from the field where a customer came with a 1300 mm shaft and we had to recommend a larger size:

• Pipes DN 80 and larger – the fittings for such dimensions are physically large and cannot be installed in a 1300 mm shaft without compromises
• A pumping assembly with a submersible pump and a large electrical box on the side of the shaft – there is insufficient space for cable routing, level switch, and controller
• A combination of water metering and inspection functions in one shaft – if the shaft is to serve two purposes, you will need more space for fittings of both branches
• A customer who plans to expand the assembly in the future – for example, to add a UV lamp, water softener, or another filter. It is better to choose a larger size now than to redo it in three years.

Diameter 1600 mm: When Space Determines Comfort and Safety

A shaft with an outer diameter of 1600 mm is the choice for situations where the installation is not a one-time job – where people will regularly enter the shaft, where the assembly is complex, or where there is simply a need for future reserves. It is also the standard size for larger pumping stations for foul water.

Pumping Shafts: 1600 mm is Almost Always the Right Choice

Pumping shafts are a different category than water metering shafts. Here, foul water is collected, sediments settle, and biological decomposition occurs. The service technician must have access to the pumps, level sensors, check valves on the discharge pipe, and the electrical installation. All of this requires enough space. Therefore, pumping shafts are primarily available in sizes of 1300 and 1600 mm.

Pumping foul water shaft MIDI 1300×1000 is suitable for smaller buildings – typically a single-family house with one toilet or a cottage. When the inflow volume increases, or when you need a duplex pump (two pumps for redundancy and rotation), it is time to choose the pumping foul water shaft MIDI 1600×1000. With two submersible pumps, their discharge pipes with check valves, float switches for three levels, and electrical panels, the interior of a 1600 mm shaft is filled to 70–80 % capacity – which is an ideal state. In a 1300 mm shaft, the same content would be at 110 % and the installation would be complicated.

When 1600 mm is a Necessity for Water Metering Shafts

For water metering shafts, a diameter of 1600 mm is necessary in these situations:

• Inlet pipe DN 63 and larger, with the assembly including a filter, water meter, pressure-reducing valve, pressure gauges, and sampling valves
• More than one pipe enters the shaft – for example, a garden branch, house distribution, and pool supply
• A requirement from the water utility or distributor for the technician to have access to the shaft for remote reading with a modem installation
• The shaft serves both as a water metering and as a treatment shaft – it contains a UV sterilizer, a filter with automatic backwash, or a chlorine doser
• Flat terrain with groundwater – where the shaft is deeper (more than 2 m) and the technician must physically enter for any service

An example is the circular PP 1600×1000 plastic self-supporting water meter chamber, which provides an internal diameter close to 1500 mm and a base area of approximately 1.77 m². This is a space where one technician can work comfortably with tools, without unnecessary struggle with valves.

Depth 1000 mm in the chamber designation: what does it mean

Have you noticed that in designations such as "1300×1000" or "1600×1000", the second number is always 1000? This number indicates the basic (minimum) height of the chamber body – i.e., the height of the standard chamber segment without extension sleeves. In practice, it is the height from the bottom of the chamber (or from the base plate) to the top edge of the body without the cover.

If you need a deeper chamber – for example, 1.5 m or 2 m – extension sleeves of the same diameter are used. These are produced in standard heights of 500 mm or 1000 mm and can be combined with each other. For example, for a total depth of 2000 mm, you use a basic body of 1000 mm + an extension sleeve of 1000 mm. For a total depth of 1500 mm: a basic body of 1000 mm + a sleeve of 500 mm.

The burial depth of the chamber is closely related to the frost depth in your region and the depth of the supply pipe. We discuss this topic in detail in the article Chamber burial depth: how to correctly place the chamber below the frost level. Here is a brief summary: in Slovakia, the frost depth varies by region from 80–120 cm, so the valves in the water meter chamber must be placed below this depth, or the chamber must be well insulated.

Chamber dimensions and standards: what the legislation says

In Slovakia, there is no fixed minimum diameter prescribed by standards for private water meter chambers in front of a domestic consumption point. However, there are recommendations and conditions from water distributors. Most water utility companies have their own operational procedures, where they specify minimum chamber dimensions for placing the water meter. Typically, they require at least 200 mm of free space on each side of the water meter and at least 300 mm above and below the water meter. For a water meter DN 32 on a pipe DN 32, this practically means: a chamber with an internal diameter of at least 600 mm is technically sufficient for the water meter, but for comfortable access and installation of additional valves, a minimum internal diameter of 900 mm is recommended – which in reality corresponds to an external diameter of 1000 mm.

For pumping sewer chambers, the requirements are stricter. STN EN 752 (drainage outside buildings) and STN EN 12050 (pumping of waste water) stipulate that pumping stations must be accessible for service and cleaning. Specific dimensions depend on the pump performance and chamber volume, but for standard pumping stations in a family house, an external diameter of 1300 mm is an absolute minimum and 1600 mm is standard.

Practical scenarios from the field: when customers regret choosing a small chamber

Over the years of work in this field, the same stories keep repeating. Here are three typical examples from practice:

Scenario 1: 1000 mm water meter chamber and subsequent reconstruction

A customer installed a 1000 mm diameter water meter chamber in 2018 as a cost-saving solution. The water meter assembly was simple at that time: one valve, water meter, another valve. In 2023, the customer wanted to add a filter with automatic flushing (body size 30 cm) and a UV lamp (40 cm). None of these could fit into the 1000 mm chamber. Result: new excavation, new 1300 mm chamber, connection, backfilling, and terrain restoration. Cost: 1,200–1,800 € depending on the location. If he had bought a 1300 mm chamber in 2018, the additional cost compared to 1000 mm would have been about 80–120 €.

Scenario 2: 1300 mm pumping chamber vs. dual pump

A customer has a cottage area with 8 cottages connected to a common septic chamber. The original 1300 mm chamber had one pump. When the pump failed, the chamber was out of service for 12 hours. The customer wanted to add a backup pump. Problem: two submersible pumps, their discharge pipes, check valves, and level sensors could not fit into the 1300 mm chamber without extreme installation compromises. Solution: new 1600 mm chamber. If it had been 1600 mm from the start, it would have cost 200–350 € more. The reconstruction cost 2,500 €.

Scenario 3: Correctly chosen dimensions – a practical example

A customer from Záhoria was building a new family house with a private well. He consulted with us before excavation. After reviewing his situation (well, hydro pump station, UV filter, water softener, and connection to garden irrigation), we recommended a 1600 mm chamber for the hydro pump assembly and water meter valves. The installation went smoothly, everything fit, and the technician could even enter the chamber after installation to tighten the safety rings himself. The customer was satisfied. Service one year later: 20 minutes of work from above, no problems.

Economy of choice: shaft price vs. excavation cost vs. cost of error

The price of the plastic PP shaft itself usually constitutes a minor part of the total installation costs. A significantly larger item is earthworks, delivery of backfill material (crushed stone, gravel), concrete foundation slab, pipe laying and fitting installation. When comparing three dimensions:

Parameter	Ø 1000 mm	Ø 1300 mm	Ø 1600 mm
Inner diameter (approx.)	~950 mm	~1250 mm	~1550 mm
Bottom area (m²)	~0.71	~1.23	~1.89
Excavation volume at h=1.2 m (m³)	~1.1	~1.9	~2.9
Relative premium compared to Ø1000	—	~+15–20 %	~+30–45 %
Suitability for service access	no	limited	yes
Typical use	simple water meter assembly DN32	standard water meter / small pumping	complex water meter, pumping

From the table it is clearly visible that moving from 1000 to 1300 mm increases the excavation and material costs relatively little – but significantly increases the comfort and flexibility of the installation. Moving to 1600 mm is a bigger jump, but still several times cheaper than future reconstruction. Therefore, we recommend the rule: choose one size larger than you think you need. The earth is dug once, the shaft will be there for 30–50 years.

Shafts for wells: a special case with different rules

If you are looking for a shaft for a drilled or dug well, the rules are a bit different. This is written in detail in the article Shaft for a drilled well: what it must meet and how to connect it to the water supply. Here only briefly: the shaft above the well serves as a protective casing for the wellhead and possible fittings. If a hydrofor assembly (pump, tank, fittings) is also placed in the shaft, then the shaft size is determined by the fitting assembly. For a submersible pump without a hydrofor assembly in the shaft, a small shaft is sufficient, while for an in-situ hydrofor assembly, the requirements for diameter are much higher.

Shaft backfill and stability: relation to size

Self-supporting plastic shafts (marked as "self-supporting" in the product name) are structurally designed to withstand lateral earth pressure without an external concrete shell. This is true under the condition of proper backfill. Manufacturers specify backfill with crushed stone (fr. 8–16 mm or 16–32 mm) compacted in layers of max. 30 cm. For larger diameter shafts (1600 mm), the wall area is larger and thus the lateral pressure is higher – so proper backfill is more critical than for the small 1000 mm diameter.

If the soil is unstable (mud, peat, high groundwater level), a concrete slab must be placed under the shaft – at least 150 mm thick. The shaft is then placed on this slab and either fixed with anchor bolts or reinforced with a concrete collar around the lower part. More on this topic can be found in the article Installation of a water meter shaft step by step and Installation of a pumping sewer shaft: what you need to know before installation.

Decision-making process step by step

If you are faced with the choice of shaft size, we recommend the following procedure:

1. Determine the type and purpose of the shaft – water meter, inspection, pumping (siphon), well shaft
2. List all fittings that will be inside – each separately with its dimensions (length, width, height)
3. Determine the diameter of the inlet and outlet pipes – DN 25, 32, 40, 50, 63, 80, 100...
4. Think about the future – do you plan to add filtration, softener, UV lamp in a few years? If yes, plan for it now
5. Check the requirements of the water distributor (if it is a public water supply) – some have a prescribed minimum internal space
6. Determine the depth of installation – at depths over 1.5 m, a larger diameter makes it much more comfortable for technicians to access the shaft
7. Compare prices – calculate total costs including excavation and backfill, not just the price of the shaft
8. Add one size extra – if it comes out to 1000 mm, consider 1300 mm. If it comes out to 1300 mm, consider 1600 mm

Most frequently asked questions (FAQ)

Can I use a 1000 mm diameter shaft for DN 50 water meter fittings?

Technically, it is on the edge of possibility. DN 50 fittings (ball valves, water meter, check valve) are physically larger than DN 32 and take up more horizontal space. With an internal shaft diameter of ~950 mm and an assembly length of 70–90 cm, you have only 3–5 cm of clearance on each side. This is insufficient for installation and service. For DN 50 and larger pipes, we recommend a minimum of 1300 mm, ideally 1600 mm.

What is the difference between the outer and inner diameter of the shaft?

The outer diameter (e.g. 1300 mm) is the total size of the plastic cylinder including the wall thickness. The inner diameter is 30–50 mm smaller (2 × wall thickness). Therefore, a shaft marked as 1300 mm has an inner diameter of about 1250–1270 mm. When selecting, always work with the inner diameter when calculating what fits inside.

Can I extend the shaft after installation?

Yes, but only if the shaft is from a modular system and it is not yet definitively backfilled and the site is not yet restored. Extension sleeves are slipped onto the top edge of the shaft and sealed with a rubber gasket. If the shaft has already been in the ground for 10 years, extension requires a complete excavation around the shaft – which is practically a reconstruction. Therefore: design the shaft depth correctly from the beginning.

Is a 1600 mm diameter shaft too large for a typical family home?

For a simple water meter shaft with basic fittings, 1600 mm is large, but not unnecessary – if you know you will be adding treatment equipment in a few years. For a pumping sewer shaft in a family home with one or two pumps, 1600 mm is ideal. Larger shafts also better dampen pump noise and provide a larger accumulation volume, which protects the pumps from too frequent starts.

What are the differences in excavation costs between diameters 1000, 1300 and 1600 mm?

At an excavation depth of 1.2 m, the volume of excavated soil for 1000 mm is about 1.1 m³, for 1300 mm about 1.9 m³ and for 1600 mm about 2.9 m³. At an average excavation cost of 25–40 €/m³, the difference between 1000 and 1600 mm is about 45–72 € for earthworks alone. Backfill material is another item, but the total difference in earthworks and backfill between the smallest and largest diameter at a depth of 1.2 m is usually 100–200 €. This is a minimal cost for significantly better comfort and flexibility for decades to come.

Do pumping chambers apply different dimension selection rules than to water meters?

Yes. With pumping chambers, the volume of accumulation (how much wastewater accumulates in the chamber between pumping cycles), the number of pumps (1 vs. redundant dual), the type of level sensors (float switches require free movement space), and accessibility for cleaning come into play. For pumping chambers, we recommend a minimum diameter of 1300 mm and preferably 1600 mm for a long-term comfortable solution. Details can be found in the article Installation of a pumping chamber: what to know before installation.

Conclusion: the chamber diameter decides for decades

Selecting the correct chamber diameter is not something to cut corners on just because of a few dozen euros. A chamber is an element that is installed once – and then lives underground for 30, 40, sometimes even 50 years. Every year, when the technician opens the cover and performs maintenance, they will feel whether the chamber was chosen correctly or not. Every time you need to add a fitting or replace a pump, it depends on how much space you left for visibility and accessibility.

Let's summarize the recommendations briefly: a diameter of 1000 mm is suitable only for the simplest water meter assemblies on small pipe diameters, where expansion is not expected. A diameter of 1300 mm is the golden standard for most single-family homes – comfortably accommodating a standard water meter assembly and a simple pumping system. A diameter of 1600 mm is the choice for more complex installations, for pumping chambers with multiple pumps, for customers planning expansion, and for anyone who wants the technician to not have to twist into unnatural positions during service work.

If you are unsure, consult before digging – not after. Also read our other articles in the Knowledge Center, for example How to choose a chamber: water meter, inspection or pumping? or Common questions about chambers and tanks for home water systems, where you will find answers to specific situations from practical experience.

Do you have a question on this topic?

Having trouble deciding or dealing with a specific situation in your home? Write to us – we are happy to help.

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