Select to expand quotedecrepit said..
My shower taps are like this, I don't like wasting water so I adjust hot and cold for a fairly low flow. But after a few minutes, the cold flow reduces, so I have to add more cold, then the hot flow reduces, so I add more hot. It takes several minutes for the flow to stabilise. My wife on the other hand likes a generous shower and doesn't have the same problem.
This is expected. The rubber gasket inside the tap expands when exposed to heat and blocks the flow off. Since you open the gasket, say only 2mm, and the gasket expands, say 1mm, you have 50% blocking of the flow. Wife open the gasket 10mm, expansion eats 1mm, only 10%, no noticeable difference in overall water temperature.
Back to the wet drip: It could be possible that the very low water pressure (water head) makes the dripper highly susceptible to small temperature changes that happen as the water starts flowing? I'm also interested in setting up a very accurate drip for cold-brewing coffee over many hours. The setups one sees in that field are also low-pressure, but use a very accurate mechanical nozzle, certainly not from the irrigation suppliers. Perhaps you could look at one of those?
If you look over history books , over thousand of years there are multiple clever mechanical water cloaks that could
very accurately dose /dispence water without ever clogging.
They are beautiful
, some are cheap some more expensive, but most could work for ages without any maintenance input,
Hi freddo,
I've done a fair bit of hydraulic testing, usually on much larger systems, and its common for it to take hours for the system to get to equilibrium. With such a slow flow rate and a large tank it could take a very long time, and every time you adjust you need to wait all over again.
For this I'd suggest a peristaltic pump. Pretty easy to set up yourself if you can find a good variable speed motor. Handles dirty water ok. But... even then 5% accuracy will be a challenge. A cheap one off the shelf would be your best bet.
If you are put on a IV in hospital the drip system used is very simple and works extremely well .
perhaps you could source one of those bag delivery systems and adapt it to your header tank.
Select to expand quoteBeaglebuddy said..
You are not using the dripper as it is designed to be used. Basically you have it almost on zero PSI or whatever you blokes use to measure water pressure. These are not designed to work at the full pressure you would find in your home's plumbing system either but rather at a reduced pressure, they sell a special pressure reducing fitting for this because full pressure tends to blow off the little tubing from the barb fittings. Your setup would be called an open system, it needs to be a closed system. It's possible if you kept a large enough head or volume of water in the tank it could achieve the correct pressure but the tank would need to be very large.
you got it right beaglebuddy. pull apart your dripper and see if has a pathway through the plastic or some kind of internal diaphram. either way they are designed for a pressurized system. if you have an unpressurized system you just need a valve. when running a long string of drippers it pays to loop the feed line back to the source to give equal pressurre in all drippers
Do you have a consistent head of pressure? ie the volume above the orifice is constant a drop in volume will reduce flow due to the reduction of mass?
on a thought tho.
Software Engineer here with a little experience in fluid design.
It's the same reason the water flow reduces or stops when you turn the hot tap on in the shower; water has an aversion to work and will always flow away from it. If this was a leak that you didn't want dripping flow would actually increase over time. Water is repelled by work and attracted to trouble.
