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I've got another question for you if that's ok. I'm not asking people to check my detailed designs, but I could really use some feedback on the principle of the method that I think I need to use... here it is:

Bojoi

It is a gravity flow system from a spring to a reservoir and then to a distribution line in a village. The system was initially designed by a Kyrgyz engineer. The diameters of pipe were chosen without information from a topographical survey. They were effectively 'guestimates' made with the help of a Tajik engineer who had some experience in gravity flow systems (the Kyrgyz engineer did not have previous experience).

The polythene pipes have all been ordered and delivered, but not yet installed. I asked the Kyrgyz engineer to perform a topographical survey which he has now done. He also measured the total flow available from the spring as 2.5 l/s (population of village ~800 people so should be ok)

The topographical information is only for the distribution network. I am trying to find out if any information is available about the section between the spring and the reservoir so I can analyse this section too (this part will be metal pipe with no tap-stands so assuming there is enough drop to get it to the reservoir, I hope there won't be problems).

The height difference between the reservoir and the last tap stand is 160m, over a distance of 4.5km. The polythene pipes are rated for a pressure of 60m (6 atm). Therefore I think the design needs two break pressure tanks so that static head in any part of the system never exceeds 60m. These were not included in the original design.

My process involved firstly analysing the original design based on 12 tap stands set to share 2.5 l/s flow, i.e. about 0.21 l/s for each tap stand. I determined head losses from the flow nomograph in 'A Handbook of Gravity-Flow Water Systems' by Thomas Jordan, and then checked these using the Hazen-Williams formula. It seems clear from the head losses calculated, that if break pressure tanks were included, the lower part of the system would experience negative pressures and therefore would not function properly. (The total head losses are ~160m, about the same as the actual total height drop, so when break pressure tanks are included these head losses cause negative pressures).

Therefore I have tried to re-design the system, using the pipes available. I have tried to keep residual head in the pipeline and at tap stands > 7m where possible (minimum recommended by Jordan). For the lower part of the system, using single 32mm diameter pipe (what is available for this part) causes too much head loss. Therefore I have suggested using two parallel 32mm diameter pipes to halve the amount of flow in each pipe and therefore reduce head losses. Is this idea practical? (Given the situation of pipes already bought and on-site). It obviously means that the system cannot extend as far as originally planned. I realise it is more complicated and will need extra connectors etc etc, but if anyone knows if this is a valid solution that would be really helpful.

In another gravity scheme (only from catchment to reservoir) the height difference between the spring and the reservoir is 250m (over a distance of 6km). Due to the land profile and the pipes available, it is not possible to install enough break pressure tanks in this system to keep all static head below the max pipe pressure of 60m i.e. 6 atm. Therefore the system would not be able to withstand static head.

Therefore I propose to avoid the possibility of static head by 1) NOT using a valve at the intake to the storage reservoir, and 2) ensuring that the overflow of the reservoir is bigger than the intake, so that the inlet always flows freely into the reservoir (i.e. discharging into the atmosphere). Is this a valid method for this scenario?

I've got another question for you if that's ok. I'm not asking people to check my detailed designs, but I could really use some feedback on the principle of the method that I think I need to use... here it is:

Bojoi

It is a gravity flow system from a spring to a reservoir and then to a distribution line in a village. The system was initially designed by a Kyrgyz engineer. The diameters of pipe were chosen without information from a topographical survey. They were effectively 'guestimates' made with the help of a Tajik engineer who had some experience in gravity flow systems (the Kyrgyz engineer did not have previous experience).

The polythene pipes have all been ordered and delivered, but not yet installed. I asked the Kyrgyz engineer to perform a topographical survey which he has now done. He also measured the total flow available from the spring as 2.5 l/s (population of village ~800 people so should be ok)

The topographical information is only for the distribution network. I am trying to find out if any information is available about the section between the spring and the reservoir so I can analyse this section too (this part will be metal pipe with no tap-stands so assuming there is enough drop to get it to the reservoir, I hope there won't be problems).

The height difference between the reservoir and the last tap stand is 160m, over a distance of 4.5km. The polythene pipes are rated for a pressure of 60m (6 atm). Therefore I think the design needs two break pressure tanks so that static head in any part of the system never exceeds 60m. These were not included in the original design.

My process involved firstly analysing the original design based on 12 tap stands set to share 2.5 l/s flow, i.e. about 0.21 l/s for each tap stand. I determined head losses from the flow nomograph in 'A Handbook of Gravity-Flow Water Systems' by Thomas Jordan, and then checked these using the Hazen-Williams formula. It seems clear from the head losses calculated, that if break pressure tanks were included, the lower part of the system would experience negative pressures and therefore would not function properly. (The total head losses are ~160m, about the same as the actual total height drop, so when break pressure tanks are included these head losses cause negative pressures).

Therefore I have tried to re-design the system, using the pipes available. I have tried to keep residual head in the pipeline and at tap stands > 7m where possible (minimum recommended by Jordan). For the lower part of the system, using single 32mm diameter pipe (what is available for this part) causes too much head loss. Therefore I have suggested using two parallel 32mm diameter pipes to halve the amount of flow in each pipe and therefore reduce head losses. Is this idea practical? (Given the situation of pipes already bought and on-site). It obviously means that the system cannot extend as far as originally planned. I realise it is more complicated and will need extra connectors etc etc, but if anyone knows if this is a valid solution that would be really helpful.

In another gravity scheme (only from catchment to reservoir) the height difference between the spring and the reservoir is 250m (over a distance of 6km). Due to the land profile and the pipes available, it is not possible to install enough break pressure tanks in this system to keep all static head below the max pipe pressure of 60m i.e. 6 atm. Therefore the system would not be able to withstand static head.

Therefore I propose to avoid the possibility of static head by 1) NOT using a valve at the intake to the storage reservoir, and 2) ensuring that the overflow of the reservoir is bigger than the intake, so that the inlet always flows freely into the reservoir (i.e. discharging into the atmosphere). Is this a valid method for this scenario?

I've got another question for you if that's ok. I'm not asking people to check my detailed designs, but I could really use some feedback on the principle of the method that I think I need to use... here it is:

Bojoi

It is a gravity flow system from a spring to a reservoir and then to a distribution line in a village. The system was initially designed by a Kyrgyz engineer. The diameters of pipe were chosen without information from a topographical survey. They were effectively 'guestimates' made with the help of a Tajik engineer who had some experience in gravity flow systems (the Kyrgyz engineer did not have previous experience).

The polythene pipes have all been ordered and delivered, but not yet installed. I asked the Kyrgyz engineer to perform a topographical survey which he has now done. He also measured the total flow available from the spring as 2.5 l/s (population of village ~800 people so should be ok)

The topographical information is only for the distribution network. I am trying to find out if any information is available about the section between the spring and the reservoir so I can analyse this section too (this part will be metal pipe with no tap-stands so assuming there is enough drop to get it to the reservoir, I hope there won't be problems).

The height difference between the reservoir and the last tap stand is 160m, over a distance of 4.5km. The polythene pipes are rated for a pressure of 60m (6 atm). Therefore I think the design needs two break pressure tanks so that static head in any part of the system never exceeds 60m. These were not included in the original design.

My process involved firstly analysing the original design based on 12 tap stands set to share 2.5 l/s flow, i.e. about 0.21 l/s for each tap stand. I determined head losses from the flow nomograph in 'A Handbook of Gravity-Flow Water Systems' by Thomas Jordan, and then checked these using the Hazen-Williams formula. It seems clear from the head losses calculated, that if break pressure tanks were included, the lower part of the system would experience negative pressures and therefore would not function properly. (The total head losses are ~160m, about the same as the actual total height drop, so when break pressure tanks are included these head losses cause negative pressures).

Therefore I have tried to re-design the system, using the pipes available. I have tried to keep residual head in the pipeline and at tap stands > 7m where possible (minimum recommended by Jordan). For the lower part of the system, using single 32mm diameter pipe (what is available for this part) causes too much head loss. Therefore I have suggested using two parallel 32mm diameter pipes to halve the amount of flow in each pipe and therefore reduce head losses. Is this idea practical? (Given the situation of pipes already bought and on-site). It obviously means that the system cannot extend as far as originally planned. I realise it is more complicated and will need extra connectors etc etc, but if anyone knows if this is a valid solution that would be really helpful.

In another gravity scheme (only from catchment to reservoir) the height difference between the spring and the reservoir is 250m (over a distance of 6km). Due to the land profile and the pipes available, it is not possible to install enough break pressure tanks in this system to keep all static head below the max pipe pressure of 60m i.e. 6 atm. Therefore the system would not be able to withstand static head.

Therefore I propose to avoid the possibility of static head by 1) NOT using a valve at the intake to the storage reservoir, and 2) ensuring that the overflow of the reservoir is bigger than the intake, so that the inlet always flows freely into the reservoir (i.e. discharging into the atmosphere). Is this a valid method for this scenario?

Regards,

Stephen

I've got another question for you if that's ok. I'm not asking people to check my detailed designs, but I could really use some feedback on the principle of the method that I think I need to use... here it is:

Bojoi

It is a gravity flow system from a spring to a reservoir and then to a distribution line in a village. The system was initially designed by a Kyrgyz engineer. The diameters of pipe were chosen without information from a topographical survey. They were effectively 'guestimates' made with the help of a Tajik engineer who had some experience in gravity flow systems (the Kyrgyz engineer did not have previous experience).

The polythene pipes have all been ordered and delivered, but not yet installed. I asked the Kyrgyz engineer to perform a topographical survey which he has now done. He also measured the total flow available from the spring as 2.5 l/s (population of village ~800 people so should be ok)

The topographical information is only for the distribution network. I am trying to find out if any information is available about the section between the spring and the reservoir so I can analyse this section too (this part will be metal pipe with no tap-stands so assuming there is enough drop to get it to the reservoir, I hope there won't be problems).

The height difference between the reservoir and the last tap stand is 160m, over a distance of 4.5km. The polythene pipes are rated for a pressure of 60m (6 atm). Therefore I think the design needs two break pressure tanks so that static head in any part of the system never exceeds 60m. These were not included in the original design.

My process involved firstly analysing the original design based on 12 tap stands set to share 2.5 l/s flow, i.e. about 0.21 l/s for each tap stand. I determined head losses from the flow nomograph in 'A Handbook of Gravity-Flow Water Systems' by Thomas Jordan, and then checked these using the Hazen-Williams formula. It seems clear from the head losses calculated, that if break pressure tanks were included, the lower part of the system would experience negative pressures and therefore would not function properly. (The total head losses are ~160m, about the same as the actual total height drop, so when break pressure tanks are included these head losses cause negative pressures).

Therefore I have tried to re-design the system, using the pipes available. I have tried to keep residual head in the pipeline and at tap stands > 7m where possible (minimum recommended by Jordan). For the lower part of the system, using single 32mm diameter pipe (what is available for this part) causes too much head loss. Therefore I have suggested using two parallel 32mm diameter pipes to halve the amount of flow in each pipe and therefore reduce head losses. Is this idea practical? (Given the situation of pipes already bought and on-site). It obviously means that the system cannot extend as far as originally planned. I realise it is more complicated and will need extra connectors etc etc, but if anyone knows if this is a valid solution that would be really helpful.

In another gravity scheme (only from catchment to reservoir) the height difference between the spring and the reservoir is 250m (over a distance of 6km). Due to the land profile and the pipes available, it is not possible to install enough break pressure tanks in this system to keep all static head below the max pipe pressure of 60m i.e. 6 atm. Therefore the system would not be able to withstand static head.

Therefore I propose to avoid the possibility of static head by 1) NOT using a valve at the intake to the storage reservoir, and 2) ensuring that the overflow of the reservoir is bigger than the intake, so that the inlet always flows freely into the reservoir (i.e. discharging into the atmosphere). Is this a valid method for this scenario?

Regards,

Stephen