i have a well dug in my land which is about 30 metres deep . it has been there for about a year and the water supply has been fine . the water is a little sandy but have a filter in line to clean water also has been fine . i check filter occasionly . the last month there seems to be little water . i have been told that a new hole should be made . could this be true or the locals want to get an earner out of me . could it be that lack of rain has lowered water table or is there anything else could be does anyone have any ideas as i dont wish to spend thousands of bart on new well if not needed

Most likely get the well blown. This will create a cavity or resivior for your water. It is silted up on the bottom of your casing. Danm rent a compressor and do it yourself. It is easy. Lower the air hose into the water as far as you can. Turn on air and stand back as it will blow out sand and water. Do for at least 2 hours. Need to tie the hose to the casing or it will come out.

Have fun. Remember to take out internal pipeing first before you start this operation.

When finished let well sit for 24 hours, lower pipe back in and pump. You night want to add 20 ft or one joint on your suction pipe. As you do this you will need to move your foot valve now on the end of your pipe to the bottom of the new piece.

I drill wells state side so I have zero Thai experiece. I think the short answer is yes you need a deeper well if your assumtions are correct. If you are looking to get by you need to understand your current static water level this is usually done by allowing the well to recover for say a few hours this process can take minutes or day and is based on the permeability of the formation and the permeability of the sandpack matrix that is your filter pack around the outside of the screen in the well. This sandpack can become pluged with fines and prevent water from entering your well fast enough and has little to do with static formation water levels (this may never happen in your soil conditions I dont know it depends on the type of filter pack in your well and the surrunding soils/clays ).
You need data to make your decision. If you have time you could build or borrow a water level sounder and determin your current static water level. Then do a falling head test to corelate the draw down at a givin flow rate. If you can find the equalibrium point you will have to limit you output to that level. You could also use a sistern/tank to help in your peak demand times. I hope this helps. Oh ya one last thing dont burn your pump up while you are having these issues it will only increase your costs.
Best, Ryan

Oh ya if your well is full of sand up to the level of the pump that is a non starter you gotta get it out! If you need to get fines out of the well I think the best way to do it is with a bailer it is a metal tube about 2" wide and 3' long with a check valve at the bottom. You bob it on the bottom of the well then haul it to the surface and dump it out. repete the process a hundred times or so until you hear/feel the firm bottom. The idea of the sand pack around your screen is that the grains naturally get "stacked" and create a natural filter over time this filter naturaly becomes tighter than the surronding smallest sands and keeps your well sand free. If the sands that are added during installation are not properely sorted or the sands around your well are flowing this may never work as designed. If you blow air or water into the well to lift sediment out of the well you will damage your already bad filterpack requiring you to surge it then bail it all over again. Again please note this is all non Thai experience and just food for thought.
Ryan

I agree with what Tiger wrote, and am no well expert but blowing and adding a 20 ft stinger should do the trick.

Tiger, they don't test the water here and from what I can pick up don't do deep wells. Here the object is water, doesn't have to be good water, only clear water. If it don't stink, is clear, and does not have to much salt to kill plants, by gum you got good water. Microbes be darn, we got water.

I have talked to a couple of folks and it is possible to get a deep well. Money is the object de resistance.

Same here with pressure. Most pumps work on 25 PSI max so really get about 20 PSI. Remember water is the focus, not pressure. There are a couple of place I have seen a regular pump and tank setup, but it is rare.

I am glad you are on here as these well questions pop up all the time. It is kinda like septic tank questions. You ought to see how they do it here. Pathetic. Some actually have room for a proper septic system but opt for French Drain things that work poorly at best or run it out on the ground. This is Thailand wide and then when cloroform is mentioned, back to paragraph 2.

Oh well not griping, I like it here or I would leave. I will protect my own drinking water.

Later.