Bends in foul drainage below ground

[Notch7]

I have always believed that no change of direction is allowed in foul drainage below ground.

However our builder we know well says that since nobody rods drainage anymore but uses power washers, building inspectors are more relaxed about allowing shallow bends below ground without requiring an means of access (IE inspection chamber, MH or rodding point).

We are starting a project next week that needs an inspection chamber moving outside the orangery and it has 3 incoming connections, the main and 2 from the same side. Can I move the inspection chamber, introduce bends to get the pipe runs to meet at the new location? The move is about 1200mm in a straight line with the main run.

TIA
Notch7

 

[^woody^]

It's nothing to do with drain jetting or rods, but a basic risk assessment as to the potential for blockages based on the use of the specific run, number of connections and the angle of change.

 

[bernardgreen]

However our builder we know well says that since nobody rods drainage anymore but uses power washers,

might be worth cosidering a different builder when looking for advice. One who gives more consideration to the future of the people living in the house than the consideration he gives to getting the job done in the easiest way for him.

 

[Notch7]

To be fair, the builder is sonebody who has done work for me for years. We build timber orangeries.

The builder was advising on a job he isnt actually doing the founds, he was commenting based on his experience of recent projects where building inspectors have allowed bends.

It's nothing to do with drain jetting or rods, but a basic risk assessment as to the potential for blockages based on the use of the specific run, number of connections and the angle of change

Many thanks -that makes sense. That implies its a judgement call, rather than a rigid specification.

 

[^woody^]

The builder was more or less on the right lines. No need to be harsh with him BG.

That's the case for extensions and small alterations, but if this was a new build or more extensive drainage, then it would tend to be a little stricter.

It is a judgment call, and most inspectors should be pragmatic.

 

[bernardgreen]

The builder was more or less on the right lines. No need to be harsh with him BG.

Pressure washing a blockage can result in pressurised sewage coming out of toilets. ( as a friend discovered a few years ago ). being able to rod a blockage is sensible

 

[Ian H]

I'm with your builder.

I'm a drain guy and I prefer to rod down and jet up.

 

[Notch7]

I'm with your builder.

I'm a drain guy and I prefer to rod down and jet up.

Thanks.

My builders comment about the jetting, was something the building inspector mentioned to him. I think his point was that there is less concern these days about rods getting stuck in drains because mostly jetting is used. Of course that doesnt mean that drainage design is allowed if it increases risk of blockages.

 

[Hugh Jaleak]

Building Control can be a lot more flexible on the use of bends underground now. the use of a bend immediately outside a chamber has been permitted for some time now, but ultimately you should still be able to get rods up any drain run for blockage clearance, should the need arise.

Pressure washing a blockage can result in pressurised sewage coming out of toilets. ( as a friend discovered a few years ago ). being able to rod a blockage is sensible

However, it is not always practical to rod some drains. With bigger diameter mains, and deep chambers, avoiding an entry if possible is always preferable. Rodding is now usually reserved for shallow domestic sewers, with the bigger stuff jetting is used, as this can be done from the surface. Rods are also pretty useless on stone, fat and scale build ups. Rods will poke a hole through fat, but wont remove it from the walls of the pipe. We use van packs, if these cannot deal with a blockage, then the truck mounted combination unit is called in.

Jetting is a complicated, and dangerous undertaking, with a risk of personal injury, never mind blowing a toilet, if you get it wrong. We have to undertake a weeks worth of training, and a refresher every 3 years to remain able to safely carry out jetting. With some pumps capable of putting out 200bar+ of pressure, you can blow the pipes apart, never mind anything else. I have seen picture of a colleague who's jetting hose did a U turn in the pipe and came back out at him, they're not pleasant.

Even working at much lower pressures, jetting a main, can still cause a bow wave of pressure up laterals, causing blowbacks. Another reason to avoid replacing open vented stacks with AAV's.

 

[noseall]

There are slow (long) radius bends available for this very purpose. Also, BC don't mind seeing a bend immediately exiting the IC. I would not however nail in a regular 45 degree bend mid run.

 

[noseall]

Here's one we did earlier....

Slo2

• noseall
• 18 Sep 2017

Slo1

• noseall
• 18 Sep 2017

 

[bernardgreen]

Jetting is a complicated, and dangerous undertaking, with a risk of personal injury, never mind blowing a toilet, if you get it wrong.

Which is the reason why any new drains ( or modifications to existing drains ) should be designed in a way that allows them to be rodded.

 

[Ian H]

I have seen picture of a colleague who's jetting hose did a U turn in the pipe and came back out at him, they're not pleasant.

I was on site with a tanker that had a frozen hose and the guy just turned up the pressure to get rid of it.

The piece that blew out hit a garage like a bullet from a gun!!

 

[Hugh Jaleak]

I was on site with a tanker that had a frozen hose and the guy just turned up the pressure to get rid of it.

The piece that blew out hit a garage like a bullet from a gun!!

Ice bullets we call them, bloody idiot wants to learn to drain his kit down properly if frost is forecast. All jetting kit has built in safety devices in case of a fault condition, but has been known for people to bypass them. When you see a picture of a bloke with half the flesh around his bottom jaw hanging off after being hit by a water jet, you don't take chances.

Which is the reason why any new drains ( or modifications to existing drains ) should be designed in a way that allows them to be rodded.

Meanwhile in the real world, as I said, this is not always achievable. With deep and/or larger diameter drainage, rodding is not always safe or practical. It requires a minimum 3 persons to make an entry into a chamber, jetting can be done by one.