Dead Legs in Water System

[vamsemicro]

Hi all,

What is the current standard for Dead leg in Purified water / WFI systems.

As per proposed rule of FDA is 6D. Is there any changes in current regulations?


Please clarify me.

[jalal29]

Hi,

new regulation are saying 2d rules, and if you can use sanitary valve (zero dead leg), it will be better for you.

[meyert]

What regulation is that? I've only heard that 2D or sanitary valves were best practice. It's impossible to meet 2D on all piping. A whole lot of sanitary piping systems would be out of compliance if they had to meet 2D. I believe 6D is industry standard, and that is based on user specifications (and engineering data) not a regulation. Typically a sanitary piping systems are designed to maintain temperature and flow.

[ssnmd]

USFDA - GUIDE TO INSPECTIONS OF HIGH PURITY WATER SYSTEMS defines Dead-legs in piping section. The statement is

One common problem with piping is that of "dead-legs". The proposed LVP Regulations defined dead-legs as not having an unused portion greater in length than six diameters of the unused pipe measured from the axis of the pipe in use.

[jiangbj]

2d ?
But in ISPE baseline, it is 3D?

[Paulus Gunawan]

Inside ISPE C & Q of Pharmaceutical Water and Steam Systems (2007), it mentions " all branch valves, which separate branch piping from the main loop, will be connected to ensure compliance with the 6-D rule". Inin WHO Supplementary Training Modules (January 2006) on Good Manufacturing Practice Water for Pharmaceutical Use Part 2: Water purification and engineering. it describes that there should be no dead legs (though allowable < 1.5 D), more stringent than the same training material issued in 2003 ; allowable , 2 D). Which one should we follow ? It is only one of physical prevention in term of pipe and fittings, as there are other prevention could be implemented.
As long as we can control and monitor, and keep the quality of purified water within limits, any rules is acceptable.

[ruthy shelly]

Hi guys!

Hope everyone's doing well. I'm totally new here. I was reading the forum re: dead legs in water system and I couldn't resist asking for a consult about my case: We're putting up a pharmaceutical manufacturing plant for non-penicillin products right now and currently we're on the planning and evaluation of the piping system for the distribution of WPU/Deionized water in our production area. The production area consists of 2 zones: 1. the liquid zone 2. dry/solid zone.The original plan was to put tap water and DI water outlets only in the liquid zone. Later on, we suggested to also put provisions for Tap and DI water outlets in all of the production rooms in the solid area (tableting, encapsulating rooms etc.)to maximize the utilization of the pipe that passes thru the solid zone and for future expansion. However, these outlets would have a separate valve to prevent the flow of water into these pipes when not in used. Would the provisions or inactive outlets and the pipes connected to the outlets still be considered dead legs since it would not be used for the meantime and will only be used upon expansion?

Bottom line: Is it advisable to put tap and DI water outlets in both liquid and solid zones?

Your suggestions will be highly appreciated. Thanks!

Ruthy Shelly
+63916-6031021

[Shahnawaz]

Originally Posted by ruthy shelly

Hi guys!

Hope everyone's doing well. I'm totally new here. I was reading the forum re: dead legs in water system and I couldn't resist asking for a consult about my case: We're putting up a pharmaceutical manufacturing plant for non-penicillin products right now and currently we're on the planning and evaluation of the piping system for the distribution of WPU/Deionized water in our production area. The production area consists of 2 zones: 1. the liquid zone 2. dry/solid zone.The original plan was to put tap water and DI water outlets only in the liquid zone. Later on, we suggested to also put provisions for Tap and DI water outlets in all of the production rooms in the solid area (tableting, encapsulating rooms etc.)to maximize the utilization of the pipe that passes thru the solid zone and for future expansion. However, these outlets would have a separate valve to prevent the flow of water into these pipes when not in used. Would the provisions or inactive outlets and the pipes connected to the outlets still be considered dead legs since it would not be used for the meantime and will only be used upon expansion?

Bottom line: Is it advisable to put tap and DI water outlets in both liquid and solid zones?

Your suggestions will be highly appreciated. Thanks!

Ruthy Shelly
+63916-6031021

Dear Ruthy,
No. it is better that PW loop must be connected to solid zone , it should be the part of distribution system with in the loop, there must not have any valve which segregate the solid zone line with distribution loop.
Thanks

[ruthy shelly]

Dear Shahnawaz,

Thanks for the quick response. I've considered your suggestion and I've discussed it to the engineering department already. But now they came up with a new concept of not putting any DI and tap water outlets in the solids zone (tableting room, encapsulation room, granulation room, perry gun room). Do you think they're concept is right?

I'll wait for your reply. Thanks a lot.

Warmest regards,
Ruthy Shelly

[ruthy shelly]

Dear Shahnawaz and anyone who can help,

Sir/s, I'll make the question more comprehensive. Listed below are the room assignments that we have in our production area. Can you please help me identify which of those require an active outlet for DI and Tap Water and which necessarily do not? Need to justify it since reckless installation of this water distribution might have problems arising in validation in the future.

Room Assignments:

Non-Penicillin Bldg.
Solids Zone
1. FBD - Fluid Bed Drier Room
2. V-Blender / Mixing Room
3. Perry Gun Granulation Room
4. Tableting Room
5. Semi-automatic Encapsulation Room
6. Dry Granulation Room
7. Wet Granulation Room
8. Automatic Encapsulation Room

Liquids Zone
1. Liquid Compounding Room
2. Filling and Capping Room.

Packaging Zone
1. Stripping Room
2. Blistering Room

Sorry for bring such a dummy about these, I'm totally a newbie. Thanks a lot. Have a nice day!

Sincerely,
Ruthy Shelly

[Shahnawaz]

Dear Shelly,


To install water line connections (either PW or tap water), first u need to see the area requirement, then go for equipment need whether CIP or COP. I would be more of help, if I could go through room data sheet along with plant lay out you can contact me via my e mail.
Thanks and best regards,

Originally Posted by ruthy shelly

Dear Shahnawaz and anyone who can help,

Sir/s, I'll make the question more comprehensive. Listed below are the room assignments that we have in our production area. Can you please help me identify which of those require an active outlet for DI and Tap Water and which necessarily do not? Need to justify it since reckless installation of this water distribution might have problems arising in validation in the future.

Room Assignments:

Non-Penicillin Bldg.
Solids Zone
1. FBD - Fluid Bed Drier Room
2. V-Blender / Mixing Room
3. Perry Gun Granulation Room
4. Tableting Room
5. Semi-automatic Encapsulation Room
6. Dry Granulation Room
7. Wet Granulation Room
8. Automatic Encapsulation Room

Liquids Zone
1. Liquid Compounding Room
2. Filling and Capping Room.

Packaging Zone
1. Stripping Room
2. Blistering Room

Sorry for bring such a dummy about these, I'm totally a newbie. Thanks a lot. Have a nice day!

Sincerely,
Ruthy Shelly

[meyert]

I will say that if you do as you described and close a valve between the main and branch and it is 6d then you probably don't have a "dead leg". A dead leg affects quality of the entire water system by providing a non-circulating water zone. What you have described is much worse in my opinion and would likely affect both the drop and system. The second you open the branch and have the use point closed, you have a dead leg. What is worse, if you didn't flush the branch line properly, you could introduce bio-burden to your whole system

I won't comment on where drops belong...it is my opinion that validation is not responsible to dictate where water drops go? You are supposed to validate that they are installed, operate and perform according to the specifications.

[ramanakumar]

colleagues new joinee here to boost some what extent.

dead leg our colleagues described 6D but how much length we can aceept.

[vamsemicro]

Tnx to paulux

In WHO, it was mentioned a limit for dead legs is NMT 1.5 D
But in USFDA, LVP regulations the same was NMT 6D (in consideration of WFI)

As on today most pharmaceutical firms are designing their water systems with 0 dead legs. But it is not possible for each point. some where there may extend to 0 dead legs.

We may follow which ever is less (NMT 1.5 D) in a worst case scenario.

[syx]

is the deadleg's limit for PW same with WFI or other types of USP water?
please give me the link for any reference... thanks in advance.

[syx]

I have got TRS 929 document. in page 63, it mentions: Deadlegs in the pipework installation greater than 1.5 times the branch diameter should be avoided.

[Ravi Dhanbhar]

Dear All
I agree with Mr. vamsemicro to follow dead leg NMT 1.5 D (Ref WHO) in pharmaceutical water system as it is generally accepted as current industry standard. Secondly I don’t find any problem in achieving dead leg less than 1.5 D because of availability ultra modern orbital weld machines which requires only 12 mm clearance on both side of weld. Practically Zero dead valves (i.e. block valve like GEMU) are available in market that too with inbuilt sampling port. Now a day many fields instrumentation like pH/cond meter/pressure sensors are also available in a manner to minimize the formation of dead leg.
As mentioned in many post of this thread it is true that there are guidelines expecting <6D, <3D & <1.5D too. The expectation of regulatory agencies is becoming more stringent day by day because of technological advancement.
Secondly it’s my opinion that it is always better to built quality by design itself rather than relaying on its control & monitoring because the risk of failure & their consequences are too bad in later case.
Dead leg NMT 1.5 D can equally be made applicable for purified water system too based on criticality of application.

However following abstract from SD-3.11 system design (ASME BPE-2007) Hope you will find this useful while constructing the system.
Dead leg is measured by term L/D, Where L –Leg extension, D-Id of pipe,
For high purity water & clean steam systems, L/D of 2:1 is attainable. However if dead leg 2:1 is not achievable with certain bio-processing equipments L/D of 2:1 or less shall be considered a target ratio & shall not be construed to be an absolute requirement. This guideline has also given tabular information on L/D for flow through Tee of various sizes with blind cap.

Regards
Ravi Dhanbhar