Infiltrometers come in many forms.  We supply three types.

Ring infiltrometers for measuring surface infiltration rate under saturated conditions. 

Suction (or disk) permeameters : used to measure hydraulic conductivity of soils under  unsaturated conditions. 

Borehole (Talsma) permeameters - used to measure infiltration rates of deeper soil layers via a bore hole.

Ring infiltrometers    Rings are constructed of stainless steel 2mm thick and 20cm high These are usually sold in sets of three rings which pack inside each other for easy transport.

A common order is for a 50cm diam ring, a 45cm ring and a 30cm ring.  This allows their use as three separate single ring infiltrometers or - by using the largest and smallest inside each other configured for use as a double ring system.  

Two water height measurement systems are available

1.(For falling head method) An oblique ruler (a scale fitted with a bubble so it can be easily installed at a 1:10 slope,  (ie water surface intersecting with the scale moves 1cm for each 1mm infiltration)

2. (for fixed water depth method)   Mariot bottles which hold the ring water level at a preset depth and indicate the amount of water  remaining in the bottle 

A demonstration video is available at   https://www.youtube.com/watch?v=4I4Y7VjsgPU

Price : Kit of 3 stainless steel rings (which pack inside each other) with oblique rulers $1050

Single rings $280, oblique rulers $30 ea, Mariot bottles (small 3.5L)$60ea, (Large7L)$90 All prices GST incl

Which infiltration  method to use?

The double ring method was developed to measure infiltration without the loss of water by sideways movement (sorptivity) as happens from a single ring. 

After 30 years experience in field measurement of infiltration, Soil Water Solutions has found that :-

a) It is nearly impossible to detect leaks between the inner and outer rings in a double ring system after it is set up.  To set them up it is ncessary to first install the centre ring , fill it, test for leaks, then install the outer ring.  hence double rings take 4x as long to set up  and (as time in the field is usually limited), you can only test a few sites with a small diameter ring.

b) the statistical error for a set of field infiltration measurements is usually proportional to the total soil area tested ie ideally maximise the number of tests and the size of the ring.

e) The purpose of double rings is to minimise the effects of water spreading sideways from the ring.  A sideways plume can account for a wet zone of as much as 2cm around the ring.   In a small ring (eg 10cm diam) this may be as much water as is infiltrating vertically.   ie result appears  50% higher.   By using larger rings, the proportion of water lost to sideways movement is dramatically reduced (eg a 2cm sideways plume  on a 40cm ring is only 10% of the total)

Moral of the story : use the biggest ring you can manage in single ring configuration and do as many tests as you can in the time available.    However, the down side is that you need a lot of water.    If you are concerned about sideways water flow, then compare results from tests using a small (eg 20cm dia) ring and a 50cm diam ring - the results should give an indication if the side flow is a significant problem and some guide how to correct for it.