SUPADIVERTA - syphonic rainwater diverter

SYPHONIC FLOW

OVERVIEW

LOW PRESSURE PVC PIPE allows multiple Supadivertas to divert to a larger horizontal PVC pipe for high volume flows. POLY PIPE is easier to work with, cheaper and generally preferred for domestic use. PVC and POLY PIPE can be mixed and matched in many situations. Most references on this page apply to poly pipe.

SUPADIVERTA’S syphonic system allows the harvesting and redistribution of rainwater at negligible material and plumbing costs, often over lengthy distances. It also solves one of the major problems confronting home owners wanting to site a large tank away from the house; the previous necessity to utilise a WET transfer system. The undesirability of WET systems is discussed on the WATER TANKS page.

Ideally, tanks should be optioned with the draw off outlet fitted a minimum 100mm above the tank's base and optioned or retro fitted syphonic fed inlets should be located at a similar height. If not using SUPADIVERTA or a suitable pre tank filtering system, sediment buildup can be rapid and a pump connected to a low outlet can draw sludge/grit. A huge number of tanks have pumps connected to gate valves fitted as low as 40mm above the bottom of the tank and many householders are unaware of their tank's outlet height or the existence of tank sediment! ONLY A DEDICATED DRAIN/CLEANING OUTLET SHOULD EVER BE FITTED AT A LOW POINT. This important recommendation is repeated elsewhere.


Did you know that annular (ring) vortices cause housing downpipes to be very inefficient due to air occupying NEVER LESS THAN TWO THIRDS of a downpipe's internal area?

SYPHONIC DRAINAGE IN BUILDINGS

REVOLUTIONARY syphonic drainage systems requiring fewer and smaller downpipes are increasingly being used in large commercial buildings, resulting in cost savings and greater architectural design freedom.
Each one metre of primed head is about 9.8 Kpa (approx. 1.47 psi) and buildings can generate syphonic flow rates up to 12 times that of gravity drainage. Once the system is primed, water is sucked into the pipework due to gravity induced velocity creating sub atmospheric pressure within the pipework and downpipes are manufactured to withstand those forces.
Well known buildings utilising syphonic drainage include Melbourne Cricket Ground, Eureka Tower (Melb), Sydney Cricket Ground, Adelaide Airport, Adelaide Convention Centre, Brindabella Business Park (ACT) and Brisbane Square.

FROM GRAVITY TO SYPHONIC

Transfer to a solid water head traps air in the pipework and the resultant air pockets need purging before optimum efficiency can be achieved. Air pockets act as physical barriers to restrict flow and the generation of head pressure but as bubbles are calved from the air pockets and the pockets become smaller, the air pockets are swept away. 19MM POLYPIPE GENERATES GREATER VELOCITY THAN 25MM PIPE FOR THE SAME VOLUME OF WATER AND PURGING (PRIMING) IS FASTER.

IT IS ESSENTIAL THAT THE VERTICAL DROPS REMAIN VERTICAL TO ENABLE PRIMING.

AQUATREK RECOMMENDS THE USE OF 19mm POLYPIPE or 20mm PVC PIPE FOR THE VERTICAL DROPS.

FLOW RATES AS SHOWN IN SECOND CHART ARE MUCH HIGHER WHEN 19mm VERTICAL DROPS ARE CONNECTED TO HORIZONTAL 25mm POLYPIPE. PVC PIPE HAS LESS FRICTION LOSS THAN EQUIVALENT SIZE POLYPIPE.

• Use 25mm x 19mm barbed reducing Tees to connect 19mm vertical drops to 25mm horizontal polypipe.
• Alternatively, use a 19mm x 19mm barbed elbow to connect the 19mm drop to a 19mm horizontal polypipe, then use a 25mm x 19mm barbed reducing joiner to join the horizontal 19mm polypipe to 25mm polypipe.
• Depending on use, second and third outlets can connect to either the same or different horizontal polypipes.

IF USING VERTICAL 25mm POLYPIPE DROPS, USE ONLY ON THE 2nd PRIORITY OUTLET AND USE QUICK PRIME.
Quick Prime is explained in the Fitting Instructions.

To learn more about syphonic drainage, a recommended site is www.hydromax.com

AIR ENTRAINMENT

The term used to describe un-dissolved air bubbles suspended in liquid. During heavier rainfall, the inlet inflow is directed to the opposite side of the reservoir. This feature, plus angling the baffles to diffuse falling water, minimises entrained air transfer to the outlets, allowing the outlets to operate at peak efficiency

FULL FLOW FRICTION LOSS CHART
30.77 METRE (100 feet) LENGTH OF STRAIGHT, FREE DRAINING, LEVEL PIPE
(19mm & 25mm polypipe, 40mm PVC)

Each one metre of head produces 1.47 psi. A quick look at the chart shows that 0.95 psi is the minimum pressure needed to generate a flow of 11.4 litres per minute through 30.77 metres of unobstructed 19mm pipe but 1.47psi is insufficient to generate a flow of 15.2 litres per minute through the same pipe. If using 25mm pipe, 1.47psi would generate a flow of about 26.6 litres per minute as shown by the chart.

NOTE: Dynamic head loss is directly proportional to the pipe length and the chart's friction loss figures would be halved for a 50 foot (15.39 mtrs) length of polypipe. Add 0.70 metres to hose length for each 90 degree elbow. Other fittings and kinks in the polypipe will result in additional friction loss.

Flow Rate	Pipe Friction Loss PSI
Litres per minute	19mm	25mm	40mm
3.8	0.12	0.04	-
7.6	0.45	0.14	-
11.4	0.95	0.29	0.02
15.2	1.62	0.50	0.04
19.0	2.44	0.76	0.05
22.8	3.43	1.06	0.08
26.6	4.56	1.41	0.10
30.4	5.84	1.80	0.13
34.2	7.26	2.24	0.16
38.0	8.82	2.73	0.20
41.6	10.60	3.27	0.23
45.4	12.37	3.82	0.28

SYPHONIC FLOW RATES - SINGLE OUTLET

Flow through pipes is determined by factors influencing friction loss and dynamic head. These factors include pipe size and length, physical barriers, fluid viscosity and temperature. Many of the tables REAL LIFE FLOW TESTS used polypipe fitted with right angle fittings and joiners.

12 & 13mm hoses are not recommended for most uses with SUPADIVERTA as friction losses through these hoses are very high. For example, a primed 12mm standard garden hose flowing at 15 litres per minute has a friction loss of 3 Kpa per metre in comparison to 19mm and 25mm polypipe which have friction losses of 0.4 and 0.1 Kpa per metre respectively. At 20 litres per minute, the 12mm hose's friction loss climbs to 6Kpa per metre.

Polypipe Size				Litres
Vertical	Horizontal	Length (metres)	Head (metres)	per Minute	per Hour	Situation
19mm	19mm	3	1.5	31	1860	To tank bottom inlet
19mm	19mm	3	1.0	25	1500	To tank bottom inlet
25mm*	25mm	3	1.0	38	2280	To tank bottom inlet
19mm	19mm	13	1.5	19	1140	To tank bottom inlet
19mm	25mm	13	1.5	29	1740	To tank bottom inlet
19mm	19mm	13	1.0	15	900	To tank bottom inlet
19mm	25mm	13	1.0	25	1500	To tank bottom inlet
19mm	19mm	37	1.5	13	780	To tank bottom inlet
19mm	25mm	37	1.5	21	1260	To tank bottom inlet
19mm	19mm	17	2.0	24	1440	Free draining (to pool etc.)
25mm*	25mm	25	2.0	38	2280	Free draining (to pool etc.)
* Quick prime is recommended when using 25mm polypipe for the vertical drop
19mm vertical with 25mm horizontal polypipe is recommended for most installations
NB: Connecting 19mm drops to a short length of 25mm pipe will have negligible effect

A steady flow of 5 litres per minute/300 litres per hour from a 50 square metre roof area servicing one downpipe is equivalent to rainfall of 6mm per hour.