[ian1965]

Hi were is the best place to obtain a RO 4040 waste water control valve Many thanks

[Ian Lancaster]

Do you mean one of these?

http://gardinerpolesystems.co.uk/all-products/pump-hose/john-guest-fittings/1-2-fittings/1-2-push-fit-in-line-valve.html

[martinw]

or you could get gate valve which offers better control but needs to be adjusted more frequently as per gaps water recommendation
http://www.wickes.co.uk/Wickes-Brass-Fullway-Gatevalve-15mm/p/420185#

[richard groves]

or you could get gate valve which offers better control but needs to be adjusted more frequently as per gaps water recommendation
http://www.wickes.co.uk/Wickes-Brass-Fullway-Gatevalve-15mm/p/420185#

When I had my 4040 set up thats what I used.
Additionally on Phil from Vyairs advice I set up a bypass around this valve with two t pieces, a length of pipe and a ball valve. Set the gate valve to its optimum pure tds/waste ratio and then you simply open the ball valve to flush and close it to produce pure.
Means you  need very rarely  adjust the waste valve again once you have found that sweet spot .

[ian1965]

Thanks