Maximum Length of Remaining Branch 2

[03180318]

We are removing the existing standpipe system from the existing domestic water piping. The remaining branch lines have been capped, but vary in the length of pipe remaining between the cap and the main. There is a concern with stagnant water in these pipes promoting bacteria and backfeeding into the main water distribution system.
Are there any regulation / codes that mandate what the maximum length of dead end water services acceptable are?

 

[quark]

When we speak of purified water and water for injection systems, it is 3D for a maximum D of 1" and 6D above 1". Note that these are just guidelines and nothing is mandated.

Regards,

 

[PEDARRIN2]

If you are talking about plumbing pipe, I do not believe there is any code restriction that dictates a maximum length of dead end pipe.

From experience, it is common to have dead ends in domestic water piping, mainly for future expansion. Even in renovation projects, it is common to leave fairly long sections of dead pipe because it is never known whether or when future renovation will require water piping in the area again.

Also, typically when installing water piping, the contractor has to disinfect the piping system. Therefore, there should be no bacteria in the dead end pipes. The only way to get bacteria in a dead end pipe would be coming from the mains, so the problem of bacteria going from the dead end pipe to the mains is probably highly unlikely.

Hope that helps.

 

[Drazen]

Unfortunately I have to disagree with Pedarrin: dead end is big source of bacteria problems as is still water generally. I don't know about common practice of leaving dead branches. In my area a common practice is not to do that!

You should avoid dead end at all, and if you have some pipe lenght left for future extension the only practicable way of retaining it (if pipe diameter is large enough to justify this action) is to make recirkulacion pipe up to end of dead branch. It can be very small diameter pipe, and it should end near some frequently used tap.

Sometimes we use to connect recirculation pipe to nearest outside hydrant (fire network valve) as regular hydrant network flushing is mandated.

 

[PEDARRIN2]

It has been my experience that if the installing contractor does his job correctly and the piping has been disinfected, the only way you are going to get bacteria in your piping is if it comes in through the supply. If the piping is not disinfected correctly, bacteria can be a problem and stagnant areas could be breeding grounds for it.

The use of providing a dead end of pipe for future expansion is a common practice. The dead end might not be very long, but it does exist.

Adding a recirculation loop to prevent stagnant water in the domestic pipe could add a lot of cost to a job. I is done for the hot water, but I have never seen it for the cold side of things.

All that being said, if there are no plans for future expansion which those dead end pipes could be used, then the pipes should be removed back to the main and capped. But if there is a possibility of expansion, you would save yourself a lot of cost by leaving them in place.

 

[briand2]

In the UK, it is simply not acceptable to leave or install dead legs on water systems. Several documents (including the Health & Safety Commission's L8 "Legionnaires disease: the control of legionella bacteria in water systems") give guidance on this matter. I have been involved with many projects where a lot of time and money has been spent identifying and removing existing dead legs.

Also, regardless of how clean your cold (or hot) water system is, the bacteria, etc that come in with the mains water supply will colonise it if there is limited water turnover, etc.

Regards,

Brian

 

[03180318]

Thanks all of you. In Canada, I still cannot find out any code or regulation regarding the limitation or avoidance dead end length of pipe on domestic......