FAQs
Traps
1. What diameter and depth of seal should my traps have?
Building Regulations state that appliances that are connected to a soil pipe should comply with the following table.
| Appliance | Diameter of Trap (mm) | Depth of Seal (mm of water) |
| Wash basin* Bidet |
32 | 75 |
| Bath** Shower** |
40 | 50 |
| Sink Foodwaste disposal unit Urinal bowl Washing machine Dishwashing machine |
40 | 75 |
| * The depth of seal may be reduced to 50mm if basin is fitted with spray taps and a flush grated waste without a plug. | ||
| **Where these appliances discharge directly to a gully the depth of seal may be reduced to not less than 38mm. | ||
2. Why do McAlpine make traps with 19mm water seal and where can they be used?
Current building regulations state the minimum depth seal for traps should not be less than 38mm. However, 19mm water seal traps have been manufactured to meet the demand for replacement traps where the original shallow seal traps were installed prior to the current regulations.
It is not uncommon in older properties for the waste from baths or showers to have shallow seal traps and discharge into an open hopper head. New 19mm water seal traps are often used when replacing the sanitaryware in these properties. This practice does not comply with current building regulations and they could be rejected if the installation comes under the scrutiny of the local authority building control officer.
3. What are the flow rates of McAlpine Shower Traps?
Flow rates vary depending on the type of waste outlet and the head of water over the waste. The configuration of the discharge pipe work will also have some effect. However, McAlpine 50mm water seal shower traps have flow rates varying from 20 to 50 litres per minute with a 15mm head of water over the waste outlet and when tested under controlled conditions. All traps meet the minimum requirements of BS EN 274-2:2002.
4. Why do I get dirty water from the sink in my washing machine?
Check that hose discharge from washing Machine loops up above the minimum height as specified by the machine manufacturer and at least to the underside of the work top for an inset sink before connecting into the sink trap.
See installation details for washing machine traps.
5. The inlet nut of the trap will not tighten on to my waste outlet?
The chances are that your waste outlet is of continental manufacture and not compatible to BS Trap inlet nut. Use T12A-F fitting on 40mm or S12A-F fitting on 32mm waste outlets to convert connection back to a compatible thread.
6. There is a smell coming from my showerwaste, what is wrong with the trap?
Drain smells can enter the dwelling under certain conditions, to ensure this is not happening check that the right trap has been installed i.e is it minimum 50mm water seal?
Has the 'O' ring on the dip tube been damaged?
Is the dip tube correctly positioned within the trap?
7. Why does water not run away in my shower?
If it is not due to the obvious reason of a blockage caused by a build up of debris, the problem could be due to backpressure within the discharge pipe. This can be because at some point the discharge pipe has retained water, which is preventing air from flowing freely through the pipe. A plumber should check the installation.
8. What is the difference between an anti-syphon trap and a re-sealing trap?
A re-sealing is designed to allow air to pass through the water seal under negative pressure but will retain sufficient water to ensure the minimum depth of seal is retained. Whereas an anti siphon trap has a small mechanical valve which opens under negative pressure. Both versions will break the syphonic action thus protecting the water seal. Note. the re-sealing trap may be noisy.
For more details see relevant pages on web site or catalogue.
9. When should I use an anti-syphon or re-sealing trap?
Generally when the waste pipe or discharge pipe from an appliance is beyond the limitations of an unvented waste pipe. Usually more critical on basin and bidet wastes.
See tables in installation details
Pipe and Fittings
1. What is the Diameter of McAlpine pipe?
McAlpine HDPE pipe is manufactured to the imperial dimensions as follows.
| Internal Diameter | 1.25 inches | 1.5 inches | 2 inches |
| External Diameter | 1.5 inches | 1.75 inches | 2.25 inches |
2. Why does my pipe not fit into Multifit fittings?
Multifit fittings should accept most plastic and copper waste pipes manufactured to suit the UK market. Check that the pipe meets the minimum requirement of either 32mm or 38mm or 50mm internal bore. It may be helpful to chamfer the inside of the pipe to remove any burr.
3. How do I fit two machine hoses into a single 40mm stand pipe?
Use V33WM fitting.
See washing machine traps and fittings details
4. Are McAlpine pipe and fittings suitable for boiling water?
Yes, providing the discharge is a gravity discharge and not pumped or pressurised.
Condensate products
1. Can I connect my condensate drain from my boiler to a rain water pipe?
It depends on where the rain water pipe is discharging. Condense is acidic and should only be discharged into a foul drain. Where this is not possible it may be discharged into a special soakaway that contains lime chippings to neutralise the acidity.
2. Where should a SOAK1GR be installed?
Soakaways should only be used in free draining porous soil and should be at least 500mm away from any footings or structural walls it should also not be in the vicinity of other services such as gas, electricity or water connections.
3. How often should I replace lime chippings in my SOAK1GR?
Lime chippings will slowly dissolve depending on the amount and acidity of the condensate passing through the soakaway. Check the level and top up if necessary when carrying out an annual boiler service.
For more information see installation details.
Air Admittance Valves
1. Why does my toilet not flush properly when valve is fitted but flushes okay when valve removed?
The problem is due to back pressure and would indicate that there is a blockage or section of pipe that is full of water between the WC and the vented section of drain preventing the free flow of air through the pipe. As there is nowhere for the air to go the water will not flow.
Valves are designed to allow air into the pipe work under negative pressure but will not allow air to come out under a positive pressure.
2. Can I fit an air admittance valve outside?
Ventapipe valves are designed for and only allowed for installation internally.
3. Can I fit my air admittance valve horizontally?
Ventapipe valves should only be installed vertically.
See installation guide for more details of Ventapipe Air Admittance Valves
WC Connectors
1. Are your Flexible connectors covered by a BS?
There is no British Standard for flexible WC Connectors. However, McAlpine flexible WC Connectors are independently certified as conforming to DIN 1389-02. BSI have confirmed that the technical content of this standard would be identical to that of a BS EN.
2. Can the Building Control Officer refuse to accept Flexible WC Connectors?
They can refuse any products that were not included or detailed on the original building control approval documents.
3. Will your Flexible connectors block due to corrugations on the inside?
The material has been stringently tested and found not to retain sedimentation of organic products or chemical substances on the inside wall of the pipe.
Since their introduction the incidence of blockages have been no more than installations using conventional materials.
Trapped Shower Gullies
1. What is the difference between TSG Gullies and MD100 Gullies?
All TSG Gullies have a flange and clamp ring, which allows a waterproof joint to be made between the gully body and the floor covering or waterproofing membrane ensuring that no water can penetrate through the structure of the floor.
2. Why does water not drain away until I lift the cover plate and dip tube?
This is indicative of a problem of back pressure. This is normally found to be due to a section of pipe between the gully and the soil vent pipe retaining water, which is preventing the free flow of air through the discharge pipe. Plumber should check out the installation.
3. What will the shower/floor gully connect to?
4. Can the top of the Gully be changed?
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