PVC Reducing Bush – 2 inch Plain to 1½ inch Female BSP

2 inch plain to 1½ inch female BSP reducing bush

This PVC adaptor brings a 1½ inch female BSP threaded connection into a compatible 2 inch imperial plain socket. The outside is the plain male side of the bush; the centre has an internal female thread. It is a useful transition when your rigid pressure pipe fitting and the screw connection you need to attach are different sizes and use different joining methods.

The distinction matters: this is not a 2 inch male BSP to 1½ inch female BSP threaded reducer. Only the smaller, internal connection is threaded. Choose it when you have a suitable 2 inch imperial plain socket to receive the outside of the bush and a 1½ inch male BSP fitting to screw into the centre. One reducing bush is supplied; adjoining fittings, pipe, solvent cement and thread-sealing materials are separate.

Connection details at a glance

Where this adaptor fits into a pond system

Pond filter bays often bring together rigid pipework and components with threaded connections. This adaptor allows a compatible male threaded fitting to connect through a larger plain socket without pretending that a screw thread and a solvent-weld connection are the same thing. It can form part of a planned transition around pump, filter or ancillary plumbing, provided the connected equipment and the rest of the fittings are suitable for the application.

Start with the two connections you actually have. If the larger receiving connection is already threaded, this bush is the wrong type. Compare our BSP threaded reducers instead. If you need a plain socket with an external male thread, see our PVC pressure pipe socket nipples. These alternatives solve different connection problems, even when some of the inch figures in their names look similar.

Imperial pipe sizes and BSP thread sizes

The two figures describe different interfaces. The 2 inch figure belongs to the imperial plain pipework connection; the 1½ inch figure identifies the BSP thread. Nominal pipe size is not simply a measurement taken across any convenient surface of the part. Compare the fitting specification and the pipework system, not just the apparent width in a photograph.

In particular, 2 inch imperial pressure pipework and 50mm metric pipework are different systems. A 50mm waste fitting is also not an automatic substitute for a 2 inch imperial pressure socket. Check the receiving fitting before ordering. If you are building a matching rigid run, our imperial PVC pressure pipe listing identifies the available pipe sizes separately from hose and waste-pipe connections.

Allow for the smaller connection

This part reduces the connection to a 1½ inch thread. It does not give the smaller connected fitting the same water-carrying capacity as an unrestricted 2 inch run. Follow the pump or filter manufacturer’s connection recommendations and avoid building a chain of unnecessary reducers just to use up existing fittings. A short, sensible layout is easier to maintain and usually easier to understand when something needs replacing later.

Plan the final orientation before making a permanent joint. A threaded elbow or hose adaptor may need room to turn as it is installed. Equipment also needs enough clearance for lids, baskets, UV end caps and service covers to open. Support the adjoining pipework so that its weight or a misaligned run is not carried entirely by the equipment connection.

Preparing the plain connection

The outside of this bush belongs in a compatible plain socket. Check the parts together before joining, and make sure you have the correct cleaner and solvent cement for the actual PVC components. Follow the adhesive manufacturer’s preparation, assembly and curing instructions. Those instructions matter more than a generic promise that a joint can be used after a fixed number of minutes, because product, temperature, size and operating conditions differ.

Keep the work clean and remove debris that could be carried into the pond equipment. Any required preparation should be completed before the adhesive is applied. Once joined, leave the assembly undisturbed for the specified period and do not put it back under water pressure before the permitted return-to-service time. The plain joint is permanent; it is not a connection intended to be repeatedly dismantled.

Assembling the threaded side

The central female BSP connection accepts a matching 1½ inch male BSP part. Begin the thread carefully by hand and check for smooth engagement. If the fitting sits crookedly or binds immediately, stop and recheck the type and size. Forcing a poor match can damage the adaptor or the more expensive equipment connected to it.

Use the sealing method specified for the mating components. A connection designed to seal against a washer or O-ring needs that arrangement to remain effective; adding excessive material to the thread is not a substitute. Keep solvent cement away from the screw connection. Where the equipment must be removed regularly, include a suitable service connection such as a pressure pipe union elsewhere in the installation.

Final checks before restarting

Refill and restart the system only after the joining materials have cured as instructed. Inspect both interfaces: the outer plain joint and the internal threaded connection. A leak at one end should be traced to that connection rather than addressed by twisting the complete assembly and stressing the other joint. Keep the adaptor accessible while you check the system under normal operating conditions.

For ordering, the key description is 2 inch plain male to 1½ inch female BSP, reference PSP081. This identifies both the reduction and the mixed connection types, helping you choose the correct part first time.