Water Tank Fittings Explained
UK Flow Centre buying guide
Tank fittings: identify the connection before choosing the part
Tank walls, outlet sizes, threads and filling arrangements vary. A good installation plans the outlet, isolation, level control and safe overflow together.
1. Start with the job at the tank
2. The usual parts of a tank installation
- Tank connector or bulkhead fitting: creates the sealed connection through the tank wall.
- Outlet pipework and isolation: lets the system be connected and maintained safely.
- Float valve or level control: manages filling, where this is the required arrangement.
- Overflow: provides a safe route if the normal filling control does not stop water in time.
Plan the connection in this order
This is a planning sequence, not a drilling template. Follow the instructions for the exact tank and fittings.
3. Examples of plain-to-threaded tank connectors
These PVC-U examples have a plain solvent-weld connection on one side and a male BSP thread on the other. They are useful only when the tank opening, wall, adjoining PVC pipe and mating female thread all suit this type of connector. They are not universal replacements for moulded tank outlets, flexible liners or flanged connections.
| Example | Use it to confirm | Do not assume |
|---|---|---|
| 1-inch | A 1-inch nominal plain connection and matching 1-inch male BSP outlet are both required. | That an existing hole or thread described as roughly 1 inch will fit. |
| 1½-inch | The tank and outlet arrangement suit this larger nominal connection. | That thread size equals a measured outside diameter. |
| 2-inch | The outlet, valve and downstream pipework are all being designed around 2-inch nominal connections. | That a larger outlet alone guarantees the required flow. |
Installation limit: solvent cleaner and cement belong only on the plain PVC socket. Use the seal specified for the BSP joint, support the connected pipework and follow the tank manufacturer's rules for drilling, wall support and potable-water materials.
4. Choose how the water level will be controlled
A mechanical float valve and an electrical float switch do different jobs. Decide what must physically stop or start the water before choosing a part.
| Method | What it does | Confirm first |
|---|---|---|
| Mechanical float valve | Uses the water level and float arm to close the incoming water mechanically. | Inlet size, available pressure and flow, mounting position, float clearance and approved use. |
| Electrical float switch | Changes an electrical contact as the level rises or falls. | Control voltage, contact logic and rating, cable length, switching levels and the equipment it controls. |
| Electronic level controller | Uses level inputs and a control panel to operate compatible pumps or valves. | Sensor type, panel function, valve or pump load, electrical protection and fail-safe behaviour. |
5. Choose by the application
- New outlet on a water tank: select the tank connector first, then match the outlet pipe and valve.
- Replacing a failed fitting: measure the hole and show both sides of the tank wall before ordering.
- Automatic filling: choose suitable level control and include a correctly planned overflow.
- Pumped system: plan isolation, pipework, protection and the pump duty as a complete system.
For regulated cold-water storage
Check the current Water Fittings requirements for the whole installation, not just the connector. Water Regs UK guidance includes a securely fixed inlet control, suitable outlet isolation close to the cistern, safe and conspicuous overflow or warning arrangements, access for maintenance and materials suitable for the stored water. Irrigation or non-potable tanks may follow a different design brief, but still need a manufacturer-approved connection and supported pipework.
Keep fill control, overflow and backflow protection separate
A float switch or valve controls filling; it does not by itself establish an acceptable backflow arrangement. For mains-connected storage, confirm the protection and any notification with the water undertaker. Water Regs UK’s alternative-supply guidance explains separation from mains water.
For regulated cold-water cisterns, its overflow and warning guidance says capacity must accommodate maximum possible inflow under fault conditions, including screen restrictions. A connector’s nominal thread size is not an overflow-sizing calculation. Use the exact tank and inlet data, manufacturer instructions and accepted installation design.
Keep a handover record of fill and low-level settings, valve/sensor identities, isolation points, overflow destination and the competent person’s safe test results. Do not defeat protection or deliberately flood the tank to test it.
Before you order: five details to send
Photograph the inside and outside of the tank wall.
Measure the hole and note the wall thickness.
Measure the pipe outside diameter and identify its material.
Photograph and identify any existing male or female thread.
Say whether the stored water is potable or non-potable.
These details prevent the most common incompatible-fitting orders. Also state the expected flow, whether the tank is already drilled and how the adjoining pipework will be supported.
Quick tank-fitting questions
Does a 2-inch connector need a 2-inch hole?
Not necessarily. The named connection size does not tell you the required tank-wall cut-out. Use the dimensional drawing or fitting instructions for the exact connector and confirm the tank permits drilling in that position.
Can I stop a leak by tightening the connector harder?
Do not keep tightening blindly. Isolate and empty the connection safely, then check the fitting, sealing faces, washer position, tank wall and pipe support. Over-tightening can damage threads, seals or the tank.
Is a float switch the same as a float valve?
No. A mechanical float valve directly controls water flow. A float switch changes an electrical contact and needs a compatible control circuit, pump or valve arrangement.
Can rigid pipework hang from the tank outlet?
No. Support adjoining pipework independently and follow the tank manufacturer's connection details so pipe weight, movement or vibration does not load the tank wall.
For installation requirements, consult Water Regs UK cold-water-storage information and the tank manufacturer’s instructions. Requirements depend on the tank, stored water and installation.
Shop float valves and level controls
Planning for autumn or winter? Check exposed tank pipework, valves and connected equipment as part of the seasonal system review.
Technical guidance from UK Flow Centre, operated by JK Irrigation Ltd. Explore all guides in the Technical Hub.
Fitting a tap or diverter to a water butt?
Our Ecosure range has ½ inch, ¾ inch and 1 inch BSP rapid tap kits, a rainwater downpipe diverter and model-specific stands. Check the exact tank outlet and supplied components first. The ½ inch kit has no hexagon bush; the other two tap kits include one.
Shop water butt accessories | Read the rainwater harvesting guide and FAQs
All these Ecosure products are collection only from Sevenoaks.
