Wiki: Waste pipe

[Tabby]

Feedback welcome...

NT

==Sizes== The (nominal) sizes of waste pipe used for domestic houses are

• 21.5mm

• 32mm (aka 1.25")

• 40mm (aka 1.5")

• 50mm (aka 2")

The actual pipe sizes vary a little between brands. The main variation is that solvent weldable pipe is one size, and non-weldable pipe for compression fittings is almost the same size, but not exactly. Just to be helpful to DIYers, both types are described using exactly the same size descriptions.

Uses of the sizes:

• 21.5mm

- overflow pipe from cisterns, not used for sink waste

• 32mm - for 1 or 2 sinks, washing machine, etc

• 40mm - can service several appliances

• 50mm - for more than 4 appliances

In practice the waste pipe sizes above are sometimes found serving more appliances than is currently building regs compliant. This doesn't usually cause a problem, and there's no legal or (usually) practical requirement to bring existing installs up to the most recent building regs.

Larger sizes also exist, and are used in flats and large houses.

==Fall== Least tendency to deposit solids occurs with a fall of -. New pipework should have a fall of - to - to comply with building regs.

Occasionally waste pipework is seen that flows '''uphill'''! Water isn't so keen on going upwards, and such arrangements tend to either not work or collect solids and be prone to blocking.

==Types of fitting== Solvent weld

• small & slim

• cheap fittings

• use solv weld pipe only, the other type wont fit or weld

• undoing a solvent weld is completely impossible, the plastic fuses together becoming one piece

• To fit, wipe the fitting and pipe clean, brush on pipe weld solvent, assemble the joint and let it set. If the pipe isn't clean, use a scourer first

• Solv weld piping soemtimes lacks access points, as no joints can be undone. Where access is needed, an access point can be included (or even a compression or pushfit tee, if preferred).

Compression

• bulkier

• more money

• often these will fit all variations of a given nominal size of pipe, but not always

• undoable

• reusable if the rubber rings are ok

• check its watertight after fitting, as its possible for the rubber ring to sit wrong and allow leakage

Pushfit

• Quick & easy to use

• Not been in widespread use long enough to establish a proven long reliable service life

• Some are easy to remove

==Compliance== New pipework must be building regs compliant at time of fitting. Old pipework need not legally meet any building regulations, current or past, and upgrades of such pipework are at the discretion of the householder.

==Blockage prevention==

1. Correct fall
2. Straight as possible runs, minimise the of use right angle joints
3. Enough access points to enable rodding the full length of the pipe.
4. Avoid putting any cooking fat or solids down the sink

Badly designed pipework with very poor flow is occasionally seen. With this, an occasional flush can help reduce solids build up, lesening the risk of blockage. This is easily done by eg filling the sink at the beginning of the pipe run to the brim, and letting it flush the pipe.

==Unblocking== [[Unblock a Drain]]

==Cutting== The main ways to cut plastic waste pipe are:

• Plastic pipe cutters - these look like giant secateurs

• Saw - most types will do it.

==See Also==

• [[Unblock a Drain|Unblock waste pipe]]

• [[Paint#Plastics|Paint waste pipe]]

• [[Water]]

[[Category:Basics]] [[Category:Bathrooms]] [[Category:Kitchens]] [[Category:Plastics]] [[Category:Plumbing]]

[Peter Scott]

Excellent start. Thank you

Cutting with a saw: Explain how to clean up and deburr the cut ends.

Compression: Undoable needs perhaps a bit extra. Where a pipe needs to be removable, for example a longish run where clogging might become a problem, a compression joint is almost essential.

Flowing uphill: Warning about long pipe runs sagging in the middle resulting in clogging. Need for careful fall and good clipping

Extra: Warnings about pipe size where eg a washing machine and a dishwasher both dischage into one pipe. Also info about the symptoms for increasingly poor flow due to clogging, eg change in sound showing that the vertical pipe is filling up before draining.

Extra: Something on clips - types, spacing etc

Peter Scott

[John Rumm]

The non weldable pipe is usually sold for push fit fittings. The compression ones are "universal" and fit any pipe type irrespective of the diameter variation.

I would no put a washing machine drain into 32mm... most stand pipes and traps for this are 40m.

Document H1 has the figures - I would suggest pinching a few of the diagrams from it as well.

You can't usually get a pushfit onto solvent weld pipe...

Its been around quite some time on waste fittings (much longer than on supply pipework. Reliability seems good.

Note pipework support needs to be better since joints could pull apart if under stress.

You said this above near enough...

Swept bends are preferable to elbow.

finer teeth make for a better job usually. Deburr after cutting though...

[Tim Watts]

Or fit some "tees" with a screw on blanking cap on the spare port, thinking logically "how would I get a rod/wire down this section of pipe?" I did that and I note that is how it is done in the loos at work (urinals and sinks).

And the possibility of incorporating an expansion joint in long (>3-4m) runs where a cm or two of movement cannot be accomodated by flexing at any bends. Plastic expands rather a lot between 0C and 90C.

Noting that virtually every type of clip has different wall-pipe distances IME so buy the same brand if that is critical.

I'm sure I will think of more after supper.

[Tabby]

Now updated, thanks folks...

NT

[[image:40mm compression fittings 4190-3.jpg|300px]]

=3D=3DPipe Sizes & Types=3D=3D The (nominal) sizes of waste pipe used for domestic houses are

• 21.5mm

• 32mm (aka 1.25")

• 40mm (aka 1.5")

• 50mm (aka 2")

Uses of the sizes:

• 21.5mm

- overflow pipe from cisterns, not used for sink waste

• 32mm - for 1 or 2 sinks

• 40mm - for washing machine, can service several appliances

• 50mm - for more than 4 appliances

Larger sizes also exist, and are used in flats and large houses.

In practice the waste pipe sizes above are sometimes found serving more appliances than is currently building regs compliant. This doesn't usually cause a problem.

There are 2 types of pipe, solvent weldable and non-weld. For a given nominal size,

• solv weld pipes are all the same real size.

• non-weld pipes are fractionally bigger

• exact non-weld pipe size varies a bit between manufacturers

• Just to be helpful, all these variations are described using exactly the same nominal size description.

• Solv weld pipe is for solv weld fittings

• Non-weld pipe is for pushfit fittings

• Compression fittings usually fit both types of pipe

=3D=3DFall=3D=3D Least tendency to deposit solids occurs with a fall of -. New pipework should have a fall of - to - to comply with building regs.

Occasionally waste pipework is seen that flows '''uphill'''. Water isn't so keen on going upwards, and such arrangements tend to either not work or collect solids and be prone to blocking.

=3D=3DTypes of fitting=3D=3D Solvent weld

• small & slim

• cheap fittings

• use solv weld pipe only, the other type wont fit or weld

• undoing a solvent weld is completely impossible, the plastic fuses together becoming one piece

• To fit, wipe the fitting and pipe clean, brush on pipe weld solvent, assemble the joint and let it set. If the pipe isn't clean, use a scourer first

• Solv weld piping soemtimes lacks access points, as no joints can be undone. Where access is needed, an access point can be included (or even a compression or pushfit tee, if preferred).

Compression

• bulkier

• more money

• often these will fit all variations of a given nominal size of pipe, but not always

• undoable

• reusable if the rubber rings are ok

• check its watertight after fitting, as its possible for the rubber ring to sit wrong and allow leakage

Pushfit

• Quick & easy to use

• Some are easy to remove

• Generally won't fit solv weld pipe

• Joints are more easily pulled apart than other fitting types, so proper pipe support is necessary.

=3D=3DCompliance=3D=3D New pipework must be building regs compliant at time of fitting. Old pipework need not legally meet any building regulations, current or past, and upgrades of such pipework are at the discretion of the householder. A lot of non-compliant pipework works satisfactorily in practice.

=3D=3DBlockage prevention=3D=3D

• Correct fall

• Straight as possible runs, minimise the of use right angle joints

• Enough access points to enable rodding the full length of the pipe.

• Where space permits, a swept bend is better than a sharp right angle

• Avoid putting any cooking fat or solids down the sink. Molten fat causes lots of blockages.

Badly designed pipework with very poor flow is occasionally seen. With this, an occasional flush can help reduce solids build up, lessening the risk of blockage. This is easily done by eg filling the sink at the beginning of the pipe run to the brim, and letting it flush the pipe.

Impending blockages are easier to clear than a blocked pipe, and can be spotted in 3 ways:

• sink drains very slowly

• outflow of pipework very slow (visible on old open drain systems)

• Trickling sound of pipework continues awhile after the sink etc is empty

=3D=3DUnblocking=3D=3D [[Unblock a Drain]]

=3D=3DCutting=3D=3D The main ways to cut plastic waste pipe are:

• Plastic pipe cutters - these look like giant secateurs

• Saw - most types will do it.

Sawn ends need the outer burr trimming off with a knife.

=3D=3DClips=3D=3D Plastic pipes sag under the load of water easily, and should be clipped to the wall. Failure to do so results in sag, with poorer flow and tendencey for the pipe to pull out of its fittings.

Different types and brands of pie clips have differing pipe to wall spacing.

=3D=3DSee Also=3D=3D

• [[Unblock a Drain|Unblock waste pipe]]

• [[Paint#Plastics|Paint waste pipe]]

• [[Water]]

[[Category:Basics]] [[Category:Bathrooms]] [[Category:Kitchens]] [[Category:Plastics]] [[Category:Plumbing]]

[John Rumm]

Typically bathroom basins...

And kitchen sinks.

Both compression and pushfit benefit from assembly with some silicone grease.

Clearing the inner burr will help prevent blockages since it stops fibres getting caught.

True for pushfit and universal - no amount of pulling will do that for solvent!

[Tabby]

Incorporated, thank you - but isn't silicone grease a bit OTT?

NT

[John Rumm]

Its not essential in the sense that you can assemble pushfit without, but I would say well worth mentioning as it makes it much easier (especially on larger stuff like WC connectors).

Some of the pushfit makers sell branded tubs of it right beside the fittings. Makers like Polypipe recommend its use in assembly. See (3) in opening section here:

it not only makes the assembly much simpler (and you are less likely to dislodge a sealing ring on a pushfit), it also improves the seal in the case of minor scratches on the pipe. Universal fittings will do up tighter and more easily with a little grease as well.

Its important to use silicone rather than other types of grease so as not to attack the rubber of the seal.

CPC sell small 50g tubes that last for ages. Some people so silicone sprays as well which can be faster to apply on larger fittings.

Much cheaper than the pipe makers branded ones as well!

e.g:

of these in the plumbing kit:

last for years.

(very good for stopping leaks on rubber seals on cars as well I find - a gentle wipe over will often stop water or wind ingress. Also for getting tight sleeves over wires and cables etc)

[Tabby]

How about I just quote you there in the article?

NT

[John Rumm]

Feel free to use whatever helps...

[Tabby]

Thanks, consider it thoroughly nicked.

NT