Would 3/4 tap give better flow than 1/2" on rainwater tank?

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I just got this large tank plumbed up using 25mm MDPE pipe. It's about a 10m run (ignore that hose it's a straight run) and 2.5m fall from the base of the tank.

I fitted a 1/2 tap since that's the adapter I could find in stock but flow is not very good. I timed 102s to fill a 6L watering can with the tank around half full.

I removed the tap entirely (push fit so easy) and filling directly from the pipe I filled it in 15s (and got myself wet).

I'm wondering if swapping to a 3/4" tap would make a significant improvement... Any thoughts? It'll take hardly any time but I'm not sure I can return these parts and they're not the cheapest so I don't want to waste more money if it won't help.

IMG_20220604_132330.jpg
 
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Obviously a 3/4" outlet will allow you fill a container quicker than a 1/2" one but, (there's always a but), it will take longer than the time when you took it direct off the pipe. Also bear in mind that as the level lowers in the tank then the pressure will also reduce and therefore start to flow a bit slower.
The more full the tank, the higher the pressure, the greater the flow. Less water, less pressure, slower flow.
 
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I've got IBCs with 3/4 hose coming off them, fill 6l in about 20secs

For the watering in the greenhouse I don't bother with cans, just go straight in with the hose off the IBC
 
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I've got IBCs with 3/4 hose coming off them, fill 6l in about 20secs

For the watering in the greenhouse I don't bother with cans, just go straight in with the hose off the IBC
Are they at ground level or higher up though?
 
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I just got this large tank plumbed up using 25mm MDPE pipe. It's about a 10m run (ignore that hose it's a straight run) and 2.5m fall from the base of the tank.

I fitted a 1/2 tap since that's the adapter I could find in stock but flow is not very good. I timed 102s to fill a 6L watering can with the tank around half full.

I removed the tap entirely (push fit so easy) and filling directly from the pipe I filled it in 15s (and got myself wet).
strange thing to get that excited over...


seriously though, I got quite anal over this very same issue a few years back. Using a wheelie bin as storage and the tap about 6 inches below the bottom of the wheelie bin I got the flow down to just under 1.5 litres per second (6 litres in 9 seconds) from a full bin.

my run starts off with a 25mm (id) flexi hose through a gentle curve then going into a 22mm (od) straight pipe (can't remember how I joined them), but it is the tap on the end that caused the big headache. I eventually went for a full bore gas fitting and formed a gentle curve with some 22mm pipe to direct the flow into the watering can.

you absolutely can not have any 90° turn like you have on yours and expect good flow, the flow needs to be as straight as possible.

xDP-3193.jpg
 
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Obviously a 3/4" outlet will allow you fill a container quicker than a 1/2" one but, (there's always a but), it will take longer than the time when you took it direct off the pipe. Also bear in mind that as the level lowers in the tank then the pressure will also reduce and therefore start to flow a bit slower.
The more full the tank, the higher the pressure, the greater the flow. Less water, less pressure, slower flow.
But my question is how much difference swapping the tap could make. The tap is reducing my maximum flow rate by a factor of about 6 which seems a lot.

Simple maths says a 3/4 tap has a cross sectional area 2.25X that of 1/2 inch but does that mean I might expect double the flow? That would certainly make it worth replacing.
 
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There’s a nasty crack in that wall.
It is but fortunately this is just an unused chimney which is likely to be removed or brought to much lower height. The structure (a hot house) used to have a coal boiler underneath
 
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But my question is how much difference swapping the tap could make. The tap is reducing my maximum flow rate by a factor of about 6 which seems a lot.

Simple maths says a 3/4 tap has a cross sectional area 2.25X that of 1/2 inch but does that mean I might expect double the flow? That would certainly make it worth replacing.
¾" tap would obviously flow a bit more water but I think you would be disappointed! it is the 90° bend you need to get rid of. Look at my set up, when this is fully open it is as fast an open ended pipe.

You need to bring the pipe in from the other side of the wood in as gentle as curve as possible, and make a straight through tap like I have done. You should be able to get close to my 1.5 seconds per litre. 10 seconds to fill a watering can is very reasonable, as good as a tradition tap on a mains supply.
 
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@Munroast I'm going to try and sort that this weekend but I wondered, did you do anything to secure the pipe on the far side? Mine is 25mm MDPE so a bit bendy. But drilling through a 100mm sleeper the friction might be enough - I could do with a little collar on the other side to lock it in place ideally
 
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I'm pretty sure I managed to force the 22 mm pipe inside the MDPE pipe then jubilee clip it., I heated the mdpe up first to make it more pliable.

You could then may be screw a 22mm tank connector into the wooden sleeper, this would hold the copper pipe well, then arrange your home made tap on the end.

if all the mdpe is under the soil it wi be pretty sturdy.
 
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Actually thinking about it a jubilee clip on the MDPE might be easily good enough to stop the pipe moving - though as you say it might be a non-issue as I do plan to bury it. Thanks.
 
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Well I have replaced this:
1655119169787.png

With this:
1655119211659.png


Removed the 90 bend and also upgraded from 1/2 to 3/4 tap. I think my watering can now fills in 20s so nearly as fast as the pipe without a tap at all, which is about as fast as my mains tap. Pretty happy with that :)
 

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