What size outlet fitting on poly water tanks

Having 4x 23000L water tanks delivered in two weeks. They will be interconnected with each bottom valve running out to a run of blueline pipe then off to the pump.

Supplier wants to know what size outlet I want. No extra cost for bigger size, 25mm is supplied standard.

25mm, 32mm or 50mm?

My thinking is the tanks will level quicker with a bigger size but does this matter. Is it worth the extra cost of associated larger fittings pre the pump.

Intend fitting a Waterboy to two of the tanks if that has any bearing.

John

I'd specify the 50mm or 32mm outlet for that size tank, reducing bushes are <$10.00 each and you've got the larger outlet if you ever need it.

32mm or 25mm piping should be fine for the inter-tank connections unless you need to equalise the tank levels quickly or you have rapid discharge requirements e.g. fire fighting water, etc.

From the picture it looks like the Waterboy comes with it's own 32mm tank outlet but you'll need to confirm it suits your tank's construction.

Thanks, makes sense.
The Waterboy supplier says they can do the larger sizes.

John

Connections joining tanks should always be fitted with flexible couplings or suitable hose. Poly tanks expand and contract as they fill and empty, particularly as they age while metal and concrete tanks are subject to ground movement.

Never fit a non flexible pipe between tanks, directly to a tank or between the tank and the pump.

How about one of the bladder tanks with fixed steel plate? I notice my plumber went PVC all the way to the inlet of my Reo Sac, and also from the tank to the pump, and wonder if that's a good idea.

I haven't seen that bladder inlet design before. The company was obviously aware of potential design weaknesses and designed the plate to overcome those issues. Full marks to them.

Their recognition of the need to protect pipe work is found on their website.

the steel mounting plate attached to the steel frame fixes the pipe location and removes any stress from the pipes. It is critical that rigid pipes are not put under stress

When you say "from the tank to the pump, are you referring to another tank or the bladder?

I'm referring to the bladder to the pump; I notice in the photo on their website, it's a flexible connection, whereas the plumber has 1.5" PVC. Only the outlet is 1" blue poly. I suspect a rigid connection to the pump may not be a good idea due to vibration from the pump.

I couldn't see a photo of a tank connection on their website. However, the website's Reo Sac Rainwater Tank Installation Instructions download states:

All Installations must conform to the Plumbing Code of Australia & NZ AS/NZS 3500 and HB230-2008 Rainwater Tank Installation Handbook.

HB230-2008 Rainwater Tank Installation Handbook is in parts an inaccurate guideline that has no legal standing.

I am unaware of any Australian Standards that state that a flexible coupling must be fitted to a tank's valve.

The water tank or bladder manufacturer's fitting instructions should always be followed so as to not void the warranty.

The link below shows a water tank manufacturer's warranty requirement for a flexible coupling fitted to an outlet valve.

http://www.bushmantanks.com.au/template ... erTank.pdf

AS/NZS 3500.1 2003 Section 11 deals with PUMPS and states the requirements for pumps used for water services to buildings.

11.4 (B) refers to the requirement for "vibration eliminators" on a pump's suction and delivery sides to prevent undue stress on the pump.

Strangely enough, not all pump manufacturers state this regulatory requirement...and this includes some of the larger manufacturers.

A cause of early pump failure happens when pumps are fitted with a 90 degree elbow directly to the pump's suction side. This can cause cavitation. While some pump manufacturers fitting instructions require that a straight length of pipe that is anywhere from 5 to 10 times longer than the pipes internal diameter be fitted to the suction side, some manufacturers do not.

Best practice should always have precedence.

EDITED on 01-08-2013. Posted installation link.

Hmm... Just looked through the installation instructions, and they do mention high pressure poly pipe on the outlet of the bladder to the pump.

May put that down on the defects list.

Just had another look and found it.

12. PUMP CONNECTION
All pumps should be installed in accordance with the manufacturer’s instructions.
The pump should be installed at, or where possible, below the outlet level to ensure ‘flooded suction’ when there is water in the bladder.
Ensure the area is flat and free of debris.
A suitable concrete paver should be used as a base to locate and secure the pump.
Ensure an appropriate power outlet is provided.
Connect high pressure poly pipe to one of the ball valves. The second ball valve is for any additional bladders connected to the system, or for a float chamber in the case of a mains water controller in a single bladder installation.