British Standard Pipe Sizes, BSP Swimming Pool Pipe

When ordering pipe for UK pools, a new construction or even the refurbishment of a pool constructed 30/40 years ago standard pipe should always be ordered in Imperial measurements, unless you have an accurate measurement that states otherwise. Standard UK swimming pool pipe for domestic installations is 1.5″ and 2″ where a larger flow rate is required. The specification for Swimming pool pipe used in the vast majority of UK pools (BS/EN1452) can be found on the following link.

BSP stands for British Standard Pipe, developed from when Britannia Ruled the Waves in manufacturing terms. BSP pipe sizes bear no resemblance to the imperial measurement they are described in. BSP (British Standard Pipe) size refers to the nominal bore diameter of steel pipe coming out of British manufacturing from all them years ago. In swimming pool terms a standard pipe diameter is described at 1.5″ BSP, the outside diameter (OD) of the pipe is actually 48.3mm nowhere near its description size of 1.5 inch. The other main pipe size for domestic swimming pool pipe is 2″ represented by an actual OD size of 60.3mm.

Confusing to say the least but there are many conversion fittings available when the pool equipment being fitted comes with metric pipe or a metric thread set. These days this is particularly apparent for the fittings supplied on the vast number of heat pumps. You can normally fit a simple 1.5″BSP/50mm socket to socket on a solvent weld to convert onto what is used in most UK swimming pools.

From our own help desk conversations many clients make the mistake of stating they have 2″ pipe on their installation when they placed a ruler and with Rack of Eye (Rock of Eye) guessed the measurement as 2″/50mm. When 1.5″ BSP swimming pool pipe is 48.3mm a close call for the inexperienced eye.

Understanding BSP Pipe Threads

In swimming pool installations, the most common type is the parallel BSP thread, sometimes referred to as BSPm that is the male type with threads on the outside of the pipe and BSPf the female versions with threads on the inside that the male fits into. With this design, the thread maintains a consistent diameter along its entire length. Very occasionally tapered BSP threads, known as BSPT, are also used, particularly in metal pipework. Unlike parallel threads, tapered threads gradually reduce in diameter towards the end. There is a misconception that PTFE tape should be used on every type of this thread. NO, only the tapered versions, more on this later **

BSP thread sizes are specified in imperial measurements, such as ½”, ¾”, 1”, and upwards. This can be confusing in countries where pipework is measured in metric units. However, many metric swimming pool pipe installation they still use imperial thread sizes for their connections. For example, a fitting designed for 50mm pipe may correctly have a 1½” BSP thread. Although this may appear unusual, it is standard practice.

BSP threads have a flank angle of 55 degrees. This is the angle formed between the two sides of the V-shaped thread profile. To establish a seal on a male to female fitting because the threads do not perform a seal in their own right, an appropriate sealing component, such as an O-ring, a flat washer or a bonded sealing washer, is usually necessary. Without a suitable sealing arrangement, BSP threads alone will not normally provide a reliable watertight joint.

**Tapered BSPT threads work differently because the taper allows the mating threads to tighten against one another and form a seal. A small amount of PTFE tape or another suitable thread-sealing compound is generally applied to help create a secure, leak-resistant connection. Top tip, do not overtighten BSPT or apply large multiple layers of PTFE tape, it is so easily done cracking the outer plastic of the thread housing. For some really technical stuff you can read the wikipedia page on this subject.

BSP and NPT Threads: Why They Are Not Interchangeable

NPT is a tapered thread system, whereas BSPm and BSPf are parallel. Although both standards use imperial size designations, their thread profiles and specifications differ. Consequently, they should not be treated as interchangeable. The difference in thread design makes it difficult to achieve a dependable seal when the two are connected. Attempting to compensate by tightening the fittings excessively can damage the threads or crack the plastic components.

For this reason, BSP and NPT fittings should not be mixed. Always identify the thread standard correctly and use compatible fittings and sealing components to ensure a safe, reliable connection.

Swimming Pool Covers

In most cases, yes — covering your pool is strongly recommended. There are two key reasons why pool owners choose to use a pool cover: safety and heat retention.

1. Safety Around Children and Pets

If you have children, pets, or frequent visitors, covering your pool is an important safety precaution. An uncovered pool can present a significant risk, particularly for young children who may be curious about the water.

A properly fitted pool cover acts as a physical barrier that helps prevent accidental falls into the pool when it is not in use. Many covers are specifically designed with safety features that can support weight and reduce the likelihood of accidents. While a cover should never replace supervision, it adds an extra layer of protection and peace of mind for families.

2. Reducing Heat Loss

A swimming pool cover with good thermal retention is another major factor. Pools lose a large portion of their heat through evaporation, especially overnight or during cooler weather. By covering your pool when it’s not being used, you significantly reduce this heat loss.

This provides several benefits:

• Lower heating costs because the water stays warmer for longer

• Improved energy efficiency for heated pools

• More comfortable swimming temperatures when you return to the pool

Even simple covers can make a noticeable difference in maintaining water temperature. With an indoor pool a full cover can reduce condensation on windows, walls and the ceiling by up to 90%

Additional Benefits of Pool Covers

Beyond safety and heat retention, pool covers can also provide other advantages:

• Keeps debris out, reducing cleaning time

• Reduces water evaporation, saving water and chemicals

• Helps maintain water balance, meaning fewer chemical adjustments

Summary

Covering your pool is a simple step that can improve safety, energy efficiency, and overall pool maintenance. For most pool owners, a pool cover is a worthwhile investment that helps protect both people and the pool itself, and a good 3rd your pocket….

Pool Covers.  A must, keep the heat in and debris out. Covers4pools For pool covers, cover rollers and liners, ring for a quote ask for Chris Benson 01904 236344 Mention this is an enquiry from Pool Experts Bolton and for your own DIY build

Choosing Pool Experts means choosing experience, reliability, and specialist knowledge you can trust.

We supply high-quality, trusted swimming pool equipment from one of the industry’s leading global brands. This ensures our customers receive durable, efficient, and competitively priced products backed by manufacturer support.

With over 20 years of experience in the swimming pool industry, we have extensive knowledge of pool equipment and maintenance. Whether you need pumps, filters, heating systems, lighting, or replacement components, our expertise helps you find the right solution quickly and confidently. It doesn’t stop there, we specialise in advice for your DIY start to finish project for the home owner. We can offer advice right from the very start of your project, covering the concrete base through to final equipment switch-on.

Based in Bolton, Lancashire, we proudly serve customers across the UK, offering dependable service and fast distribution.

We supply both domestic and commercial clients, meaning whether you’re maintaining a home swimming pool or managing a larger commercial facility, we understand your requirements and deliver products that meet professional standards.

At Pool Experts, we combine industry knowledge, trusted products, and customer-focused service to ensure you get the best solution for your swimming pool needs.

We are DIY equipment and information experts. We inform you and advise you on what the pool industry won’t tell you. It’s not Rocket Science.

The main points to consider with any DIY pool build

• Final volume of water you will have in your pool vessel. This is the starting point for correct sizing of the pump and filter.
• Pump type
  • Single speed
  • the more efficient variable speed.
• Are you having heating and what type. With these 2 factors you can calculate the time required with the heater output and balance filtration time for the desired pool temperature. You heat as you filter, the circulation pump creates flow through the filter vessel and then through you heating circuit. On the vast majority of installations, a 2nd pump is not required.
• Filter type
  • Standard HDPE plastic for filtration with no heating around 2bar spec.
  • Traditional fibre glass bobbin would with higher pressure and temperature specification around 2.5bar.
  • HDPE high efficiency 2.7bar.
  • HDPE High temp and pressure 4bar.
• Depending on pool water volume again pipe diameter can then be set, normally 1.5” and 2” for most domestic pools.
• Skimmer and drain capacity. Number of return jets.
• Sanitation type
  • Standard chemical chlorines/Bromines
  • Salt chlorination
  • UV