diameter of water pipe (too much pressure?)

[thing31]

Hello

I’ve just bought a 4 Rai land, about 200 meters long (600 feet), the upper half is sloping. I want to install a water pipe system (for garden, shower, house taps etc) connected to the village water system. The meter will be at the top of the land. I wonder if I should buy simply small diameter pipes (½ inch) for the main pipe that will go down until the end of the land, or a bigger diameter (example 1 inch). I'm just worried there is too much pressure in the small size pipe due to the slope, and get leaks … Thanks for your advices ????

[Pib]

Pressure exerted on the pipe will not noticeably change based on diameter of the pipe.  Best to buy a 1 inch pipe so you'll have more water capacity...and the larger diameter pipe will reduce loss of pressure due to friction.

[Morakot]

A half inch pipe as a main incoming pipe is not ideal. You need at least 3/4'', ideally 1'' if you're watering your garden and using household appliances at the same time.

 

Changes in pressure due to the slope should reflect the thickness class of the pipe 8.5/13 rather than the nominal size.

 

 

[thing31]

Thank you very much Morakot ! it is very helpful !

 

Sure, I get your point, better to start with a 1 inch.

When you write 'Changes in pressure due to the slope should reflect the thickness class of the pipe 8.5/13 rather than the nominal size.', do you mean I should buy a 13 class on the lower (and flat) part of the land, as there will be more pressure than on the slope (again, the connection with the village pipe will be at the top of the slope), whereas on the slope a 8.5 class should be fine? 

 

By the way do you have a good brand of pipes to recommend? I guess the cheapest ones quality is not great.

 

[sometimewoodworker]

1 hour ago, thing31 said:

Thank you very much Morakot ! it is very helpful !

 

Sure, I get your point, better to start with a 1 inch.

When you write 'Changes in pressure due to the slope should reflect the thickness class of the pipe 8.5/13 rather than the nominal size.', do you mean I should buy a 13 class on the lower (and flat) part of the land, as there will be more pressure than on the slope (again, the connection with the village pipe will be at the top of the slope), whereas on the slope a 8.5 class should be fine? 

 

By the way do you have a good brand of pipes to recommend? I guess the cheapest ones quality is not great.

 

The 8.5 pipe will be fine for the first few years but all PVC pipe degrades in direct sun so after a few years it may go brittle and loose enough integrity to break. The 13.5 has a greater wall thickness so will last longer.

 

I don’t know of any cheaper lower quality pipe available.

[KhunBENQ]

1 hour ago, thing31 said:

I should buy a 13 class on the lower (and flat) part of the land, as there will be more pressure than on the slope

13 bar! I doubt that the village water will come any close to 8.5 not to speak of 13.

13 bar corresponds to a water column of 130 meter height.

I would use 1 inch 8.5 bar standard pipes.

Are you confident that the village water is steady pressurized or did you already plan for a tank and pump?

Water pipe is the least concern in regards to cost.

 

[VocalNeal]

7 hours ago, sometimewoodworker said:

but all PVC pipe degrades in direct sun

Which is why exposed pipe should ideally be painted. 

 

[GreasyFingers]

The Tessabaan has just installed a new 50mmm main along our road. The problem is they used 18mm connectors into our 25mm pipes. The neighbor across the road had a small section of 12mm pipe in their connection.

 

No need to worry about physics.

[thing31]

Hello all

 

Thanks a lot for your valuable suggestions. Yes, you're right, 8.5 class should be enough. I will think more about 1 inch & 1/2in or everything with 1/2 inch...

Have a nice day

 

[sometimewoodworker]

3 hours ago, thing31 said:

Hello all

 

Thanks a lot for your valuable suggestions. Yes, you're right, 8.5 class should be enough. I will think more about 1 inch & 1/2in or everything with 1/2 inch...

Have a nice day

 

A 200metre run of ½” pipe is going to give you some horrendous friction losses at a reasonable flow rate of 19 litres per minute over that distance you will get around a 30psi drop,

a 1” pipe will drop about 3psi over the same distance and

a 2” pipe will drop about 0.12psi

 

these figures are extrapolated from a chart giving figures for 100’ of pipe, assuming that for 6 times the length you will have 6 times the losses 

[mahjongguy]

Why not 3/4" then?

[sometimewoodworker]

6 hours ago, mahjongguy said:

Why not 3/4" then?

Because the friction losses are a little over 3 times greater than 1” pipe

 

The optimal size depends on the flow rate you want to achieve, 19L per minute isn’t very much, if you want a much higher throughput then you could well want an even bigger diameter.

 

without a little more information it’s difficult to give a good answer.

[mogandave]

On 12/12/2019 at 5:14 PM, GreasyFingers said:

The Tessabaan has just installed a new 50mmm main along our road. The problem is they used 18mm connectors into our 25mm pipes. The neighbor across the road had a small section of 12mm pipe in their connection.

 

No need to worry about physics.

If it’s just the connection it won’t make much of a difference.

[Pib]

1 hour ago, mogandave said:

If it’s just the connection it won’t make much of a difference.

 

Well, it will make difference if needing to use water from the main soi line "without a storage tank/pressure pump" as reducing the size anywhere along the way--like right at the pipe input--will reduce water flow/capacity/pressure as illustrated below. 

 

Although nozzles are being shown a nozzle is nothing more than a smaller diameter connector....some restriction along the way...like where a small home water line hooks in the large main soi water line.  Or maybe think of it as a kink in the water hose.

 

I know in my Bangkok moobaan the lines leading from the main/large soi water line use 20mm (3/4") and 25mm (1") connectors/pipes from the soi line into the water meter....the water meter is a 20mm input/output device.  So, since the soi water line pressure is low to begin with (around 10-15psi/1 bar) in my moobaan there is no significant pressure to overcome/make-up for water flow reduction due to restrictions....like a 20mm connector.  But that don't bother me because I us a water tank/pressure pump setup to feed the water to my residence....heck, I could get by with a 1/4" water line feeding my home as I just need enough water flow/pressure to keep the tank full...top it up.

 

The great majority of Thailand main soi water lines are low pressure and not meant to feed a residence "directly" (yes I know it still commonly occurs); the soi lines are meant to feed/keep a residence water tank filled...then a water tank feed to residence pressure pump which then feeds higher pressure water to your residence. 

 

This of below picture as the main/large soi line being on the left and the nozzles/orifices representing whatever connector/line size is used to feed your residence.

 

https://techblog.ctgclean.com/2012/03/reducing-flow-vs-reducing-pressure-which-is-it/

[mogandave]

22 hours ago, Pib said:

 

Well, it will make difference if needing to use water from the main soi line "without a storage tank/pressure pump" as reducing the size anywhere along the way--like right at the pipe input--will reduce water flow/capacity/pressure as illustrated below. 

 

Although nozzles are being shown a nozzle is nothing more than a smaller diameter connector....some restriction along the way...like where a small home water line hooks in the large main soi water line.  Or maybe think of it as a kink in the water hose.

 

I know in my Bangkok moobaan the lines leading from the main/large soi water line use 20mm (3/4") and 25mm (1") connectors/pipes from the soi line into the water meter....the water meter is a 20mm input/output device.  So, since the soi water line pressure is low to begin with (around 10-15psi/1 bar) in my moobaan there is no significant pressure to overcome/make-up for water flow reduction due to restrictions....like a 20mm connector.  But that don't bother me because I us a water tank/pressure pump setup to feed the water to my residence....heck, I could get by with a 1/4" water line feeding my home as I just need enough water flow/pressure to keep the tank full...top it up.

 

The great majority of Thailand main soi water lines are low pressure and not meant to feed a residence "directly" (yes I know it still commonly occurs); the soi lines are meant to feed/keep a residence water tank filled...then a water tank feed to residence pressure pump which then feeds higher pressure water to your residence. 

 

This of below picture as the main/large soi line being on the left and the nozzles/orifices representing whatever connector/line size is used to feed your residence.

 

https://techblog.ctgclean.com/2012/03/reducing-flow-vs-reducing-pressure-which-is-it/

Did you read the article?
 

A better representation of attaching to a main and running pipe to one’s home 100m away would be a nozzle on both ends of a long pipe, both ends restricting flow. The frictional loss in the long pipe is significant, the frictional loss in the fittings not so much. 
 

To be clear, I didn’t say it would make no difference, I said it wouldn’t make much of a difference. Clearly it would be better to have 1” fittings to 1” pipe. 

 

 

[shaemus]

On 12/12/2019 at 8:16 AM, thing31 said:

Thank you very much Morakot ! it is very helpful !

 

Sure, I get your point, better to start with a 1 inch.

When you write 'Changes in pressure due to the slope should reflect the thickness class of the pipe 8.5/13 rather than the nominal size.', do you mean I should buy a 13 class on the lower (and flat) part of the land, as there will be more pressure than on the slope (again, the connection with the village pipe will be at the top of the slope), whereas on the slope a 8.5 class should be fine? 

 

By the way do you have a good brand of pipes to recommend? I guess the cheapest ones quality is not great.

 

Use a hdpe pipe. 

 

Go to global house and look at the fittings on the wall is a sample board of the different types/sizes etc. 

 

Burying pvc is asking for trouble in the future... 

[AsianAtHeart]

I agree with mogandave--tried to like his post but the forum gave me an error message for it.

My uncle is a civil engineer and I have done literally hundreds of hours of work with him on various kinds of pipe, from steel, to PE (polyethlene), to PVC (very little though, as this is not used for commercial projects)--mostly steel.  One thing I heard him say more than once is that the restriction of flow through a valve had a negligible impact on volume of flow.  One big reason for this is the Venturi effect, where the flow will speed up as it passes through a narrow restriction.

 

The illustration is somewhat accurate, but misleading.  This is because water, like electricity, will take the path of least resistance.  Given three outlets, all at the same time, the water would act much as depicted.  But if the two larger outlets were valved off so that only the smallest nozzle remained, the water would flow in much greater quantity through it.

Regarding the OP's pipe question, I would also recommend the larger diameter pipe, but for a different reason entirely.  The larger pipe will have a greater surface area for the glued joints, which will mean the joints are more likely to hold together without special thrust blocks or pouring them into cement.  The pressure is not so much a concern in terms of the pipe bursting, but rather in terms of the joints not holding together.  In this part of the world, most who work on the pipes will not glue them carefully to begin with, and joints are often the weakest point.  If glued properly, with a sufficient joining pressure that is held for at least 60 seconds before releasing it, there should be greater stability.  

 

One way of avoiding the pressure problems and the joint issues might be to consider getting a roll of HDPE (high-density PE) pipe instead.  It's good stuff, which is why the municipal water suppliers like to use it.  It does have special joining techniques, however, and is not so versatile in home use.

 

If the head on the water (drop in elevation) is sufficient to have over 80 psi of pressure at the bottom (~185 ft./55 m. elevation drop), you might need a pressure-reducing valve.  This is NOT accomplished by passing the water through a small orifice, because the static pressure when water is not in use will still climb to the level calculated by the head.  Furthermore, at high pressures, sudden valve closures may set up water hammer in your pipe and that certainly could cause it to burst.  At high head, therefore, a pressure relief valve may also be warranted.

 

Hope this helps.

 

[David B in Thailand]

Shaemus and AsianatHeart are giving the OP a good tip to consider HDPE pipe. He can also pay a minor extra fee for a larger water meter. It is only a one time fee to have a larger water meter so he has the ability to draw more water from the PWA line serving his property.  HDPE connectors are widely available in Buriram. 

[Morakot]

On 12/12/2019 at 8:16 AM, thing31 said:

When you write 'Changes in pressure due to the slope should reflect the thickness class of the pipe 8.5/13 rather than the nominal size.', do you mean I should buy a 13 class on the lower (and flat) part of the land, as there will be more pressure than on the slope (again, the connection with the village pipe will be at the top of the slope), whereas on the slope a 8.5 class should be fine?

 

Sorry, I just saw your reply now. Whether you need 8.5 or 13 depends on how steep the slope is.

 

For example if water comes in with 3 bar and your house is 55 metres lower than where the water comes in, than 8.5 will NOT be sufficient.  You need to add one bar for each 10 metres vertical drop, plus 5 bar for in coming pressure (spikes). (Try not to mix different thickness classes; it's not very practical.)

 

If the slope is too steep, you can also look into installing pressure reducers at certain points. This might be more cost effective then increasing the thickness.

 

WP says that sunlight can effect the pipes over the years. Yes that's correct. An inexpensive and effective way is to paint them where they are exposed.