Float Valve for maximum Polytank level

31 Dec 2005
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United Kingdom
Hi all,

I have a 70 gallon polytank (320 Litres)


As I understand it the 320 Litre line is up to the ball valve float rather than the actual top of the tank

When using a conventional 1/2" or 3/4" ball valve with a 4" or 6" football shaped float on them this means there is always going to be a significant gap at the top of the tank.

I need to get the max possible amount of water in this tank so I need a different type of float/ball valve

The valve has to have a 3/4" BSP male thread on it (as they allways do) and not a 1/2" thread

I would prefer a plastic fitting and it has to be very low pressure so it will accept the water as fast as possible...it also has to be mounted horizontaly through the side of the tank as they are in a conventional loft tank situation..the ball would need to be small, flat or semi flat.

I have seen these but I dont think they level out flat when the water height is reached and the inlet pipe is above the actual float. I am unsure if they are low pressure or high pressure..however the acual float is a nice and low diameter

"3/4" Float valve Assembly"


Anyone any ideas please?

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Most of these kind of things are rated on their max volume and not the useable volume.

I expect problems fitting a 3/4' valve. Better fit two 1/2' valves!

LP and HP refers to the supply pressure. Normally HP now.

Fit two tanks if you want more volume!

Thanks Tony...the system is already built so cant fit another tank or another valve...im looking for a low profile ball valve as of the original post
I think you are going to have problems then!
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This is not a conventional plumbing system that I am building. The tank in question empties completely via text message command then refills again on text message command using solenoid valves and pumps. The float valves on the system are for mechanical back up against electronic failure I am looking to get every last drop inside the 70 gallon coffin tank ( want to use coffin tanks) as I dont want to upgrade to a 100 gallon tank...the only thing restricting this is the ball valve float...so I am sure somewhere there is a low flat shaped float somewhere or a different type of float valve

So its another unattended ganga farm then! That will explain why you hide your location.

Regardless, I expect you will still have difficulties.

Why not dump the water more often?

What do you use to receive and interpret the text messages?
It cant dump the water more often as it is using the mix within the main reservoir to feed the plants (hydroponics not soil) i.e the more they feed the more the main reservoir level will drop so the more I can get in here then the longer there will be before needing to top up the main reservoir, empty it, refill it etc all by phone commands.

I am using a custom made 24 input, 24 output and 4 x analogue input board with GSM controller all custom coded (approx 10000 lines of code and 200 labour hours)
So its another unattended ganga farm then! That will explain why you hide your location.

As I have mentioned before one of my friends from school has owned a hydroponics shop for 16 years he gave me the idea for the phone controlled system of which is perfectly legal to design, build and hopefully sell in the future...google hydroponics and you will find masses of hydroponics companies within the UK (650 conventional shops not including the online traders)

I am in Christchurch, Dorset
Why don't you mount the float valve above the tank to acheive the level you want. Then raise the lid to suit.

We have concrete cattle drinkers in the fields which fill to the brim.
Thats because a portion of the drinker is raised to accomodate the float valve.
Like this....
You are not giving the info to enable to best advise you.

If you are pump feeding the tank then a float level switch on the pump will give the max volume.

If gravity feeding then a solenoid valve off the switch!


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