Pipe Size for Garden Taps

[kristen]

I want to run some underground pipe around the garden so we aren't lugging hose about to water the plants.

We have 3/4" hose 'coz the water only trickles out of 1/2" hose once I've strung several lengths together (I must do a bucket-fill timing comparison because I think the results will be surprising)

But 2 x 50M lengths of 3/4" hose connected together is jolly hard work pulling around the garden ...

So, I plan to install permanent MDPE pipe (planning on getting a trenching machine in). Ideally I will use a rainwater harvested tank in the future - with a mains-powered pump. (Or I could do that at present, just using the barn gutters, and have a mains-refill to the tank, this would suit me if a pump will give me more flow rate than mains, as that would reduce time spent watering

I have 2 x 50M of O/D 32mm MDPE at present, and I will need another 100M for a total of 200M run.

1) Is 32mm big enough to avoid pressure loss? (Lots of hand-watering of individual trees, so the faster the flow the better)

2) If I run a 32mm "backbone" down the garden, and Tee off it for each tap, can I use 25mm for that?

Reason being that I can find 32-25-32 reducing Tees, which saves a bit over 32-32-32 Tee and then a straight 32-25 coupling. The only taps I can find have a 25mm connection

I will site some taps 20M at right angles from the backbone. This will mean that all parts are reachable from a tap with 50M of hose

3) Can I use a plastic fitting for the back-plate to the tap? £5 each instead of £12 for brass? or are there longevity issues?

Plastic:


Brass:


Or can I just use a threaded elbow? (strapped to a post) That removes the need for any reducing-coupling as I can go straight from 32mm to 3/4", and will save another £5


4) Do I need a 3/4" tap, rather than 1/2", to try to maintain flow rate? or is a 1/2" tap inconsequential in the overall scheme of things?

1/2" tap and back-plate is £11.50, 3/4" is £15.00 (no double-check as this is all outside an existing double-check valve)

I was planning to put a drainage Tee at the lowest point so that I can drain the whole circuit in winter.

Any relate advice would be welcome

[Alan]

http://www.marley.co.nz/webfiles/MarleyNZ/files/MarleyPressureManualPart1.pdf

This one look at page 14 for a calculator.

http://www.philmac.com.au/library/3.2_GPS_install_tech.pdf


Plastic fittings for taps  / threaded elbow will out last brass if you insulate or drain down in the winter.

Why not drain system in winter by removing feed connection and purge with a small air compressor.
No need for low level drains. Just walk round purging from each tap.


Regards

Alan

[Justme]

Plastic fittings for taps  / threaded elbow will out last brass if you insulate or drain down in the winter.

When we bought our last house the previous owner had fitted those all around the barns & yard. Every one of the was stuffed due to cross threading & over tightening. They only dint leak due to the low water pressure & lots of PTFE tape. When we uprated the system to mains pressure we had quite a few blow off plus then later when is use even more of them went. That said I have fitted a few & they have all been ok as I was already aware of the threading & tightening issue.

[tony.]

We regularly install wash water points on our sites, these are basically hose points protected by the elements by a small box and powered from a boosted water supply.

We use 25 mm mdpe for the underground pipework, noting any joins on a drawing.
We put a water pipe tape above the pipework about 150 mm below the finished level to prevent accidents in the future.
We always fit an isolator below the tap to prevent freezing
We use metal fittings for hose points as those using them dont normally take the best of care.
Remember to get the pipework buried to a decent length to prevent freezing.

And where you come up out the ground some climaflex or similar insulation to prevent freezing.

And if you are thinking about using it via the mains supply and not just tank, a double check valve should be fitted.

Try screwfix for fittings.
We buy ours from RS as its next day delivery.

Tony

[DonL]

Hi Kristen
I put rainwater harvesting on the barn and put the IBC's a couple of metres up so I could use the narural head without a pump. The water is ditributed in 25mm MDPE pipe to 3/4" taps. The result is satisfactory for us and I'm sure the tap size is important. If you like I'll put a bucket under one of the taps and measure the flow rate. Obviously you can't operate sprinklers or anything of that sort without a pump but for simply supplying water near where you want it this is cheaper and more reliable.
I suspect you'd see little difference between 25mm and 32 mm as the main pressure drop is in the tap? but the calculater recommended above will tell you if that is true.
Don

[Baz]

I have a ball valve tap that is so much better than a normal one. Quater turn instead of all that twiddling. Not seen them in the Uk - I got it in portugal where they seemed to be standard.

[Iain]

Hi kristen
BES do loads of ball valves, I am sure there will be something suitable or you can adapt. As Baz said much easier and full bore flow.
One example below, but loads of others:-

FULL BORE LEVER BALL VALVES, WRAS APPROVED

Compression

   Full bore compression brass lever ball valves, nickel plated, red handled, WRAS approved.
Max pressure: 25 bar.
Max temperature: 65°c.
Part No.   Description       Unit Price   Qty
19565    15 mm lever ball valve   £2.93    
19566    22 mm lever ball valve   £4.36    
19567    28 mm lever ball valve   £6.71    

or
http://www.emmeti.co.uk/products/ball-valves/outdoor-ball-lever-taps
Iain

[DonL]

A little caution perhaps? There was another thread not too long ago which showed pictures of ball valves which split due to the water in them freezing last winter.
Plastic ball valves are available but expensive.
Don

[hiccup]

Hi Kristen

Take a look at www.pipestock.com

Cheapest MDPE fittings I could find and good quality. Very good range.

I'm just in the middle of assembling my water distribution "manhole" that I've built as part of my irrigation scheme. It will be mains fed for now but plan to make it tank fed in the near future so have already laid the pipes for tank and a duct for the cables.

So far I have about 8 20mm mdpe plastic ball valves in there and plan to drain down in winter if there is any chance of frost damage but hopefully as it is all underground it might be OK.

Regards

Hic!

[clockmanFR]

32mm pipe, use plastic fittings at all times, i recommend Plasson as these can be just hand tightened, from builders merchants etc.

Depth of main 32mm pipe just below double spade depth. (do not make work and mess with a mindigger) My 32mm stands on the wall all year and includes -25c in the winter.

If you go to re-use water gravity system then 32mm up to 300m still works with a 1m head.
Have fun.

[guydewdney]

I have a similar system - a ring main of 32mm, with tees off to 1/2" (15mm copper pipe) hose or large solenoid valves. Pump is a 1.5kw sub pump though.... I flood irrigate, as the mucky water blocks smaller jets.

[kristen]

Thanks very much chaps.

Noted that the plastic threads are liable to cross-thread.

I like the idea of quarter-turn "taps", I get fed up fiddling with the many-turn taps that we do have, and the few quarter-turn ones we have are a joy by comparison. My plan is to drain-down during winter, to avoid the faff of insulating the risers etc. so there won't be any issue with freezing.  I don't have an airline though, sadly ...

I looked at the calculator, but I'm afraid I don't know how to interpret the results.

A line from 25mm through a flow rate of 10 L/min gives flow velocity of 0.2 m/s, and hydraulic gradient m/100m pipe of 0.5

32mm and same flow rate gives 0.2 m/s and hydraulic gradient of 0.2

I tried to calculate the net effect of 1/2" vs. 3/4" tap, but my figures suggested that 1/2" was better, which is clearly wrong

I found this article
http://www.winsfordwalledgarden.com/development.aspx?Group=development&Page=irrigation
which says that a 50M length of 1/2" hose will fill a 2 gallon bucket in 2 minutes, whereas 50M of 3/4" hose will only take 25 seconds.

I will get some "water pipe below" tape.  On a memorable boy's-toys JCB-hire-weekend a few years ago I went through the mains, phone and electricity!!

I had already looked at http://www.pipestock.com/, thanks. I found that http://www.cityirrigation.co.uk/ were cheaper. Generally the MDPE stuff was within a penny, but their taps / valves were cheaper, and they have all the Hozelock and Micro-irrigation / Drip stuff I also need, which will be a one-stop shop, and bulk up to save some carriage.

"do not make work and mess with a mindigger"

Heavy clay here, already set like concrete, don't fancy digging a 200M trench  However, when I went through the BT line a local chap came out with a trenching machine and made a very tidy job (picture attached below). Only daftness was that he had no straddle-and-backfill device, just a bulldozer blade on the front with lots of back-and-forth to backfill at 45-degrees.

Guy: Do you know what sort of flow you get off your 1.5kw pump?  I might just be tempted to run this off a pair of IBC's to get a good flow rate, i.e. using them as a buffer and refil them (more leisurely) from the mains.

Sorry, forgot to ask before, does anyone know about Geka hose fittings?  I'm interested to know if the work better than the Hozelock type, and how they couple?. Thanks.

I presume you have to jubillee-clip a male to the hose? Will two of those just mate?


Then there is this type of fitting, I can't work out if this crimps the hose like the Hozelock ones do, avoiding the jubilee-clip? Or maybe its just for inter-connection to Geka & Hozelock? ... I've Goggled extensively and cannot find any useful "this is how it works" articles on Geka fitting


and then there are Male & Female BSP fittings. But maybe they are just to fit on to taps etc?

[Baz]

I like the look of the geka fittings. If you look at the blanking fitting http://www.easywatering.co.uk/acatalog/Geka_Blanking_Plate.html you can more easily see the ledge around each fitting that the 'prongs' engage with.

[guydewdney]

I only use geka - have a look around, there are some rip off shops on tinternet.... you should be paying about 2 quid each. much much tougher than hozelock carp. Cant undo under pressure though. They work better under pressure, as the water pressure self seals them. My low pressure ones sometimes leak a bit.

use oetiker clips, not jubilee clips, as jubilees have a sharp edge where the screw is and you keep getting your hands cut. oetiker or ear clips are once only -  you tighten them with a pair of pincers (you squash the ear from a [ shape to omega shape....)
eg
http://cgi.ebay.co.uk/5-X-OETIKER-SINGLE-EAR-O-CLIP-INSERT-RING-OC16-/200606730897?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item2eb517ca91


also see lbs horticultural for bits - you have to register as a business though - we just said we were a market garden.


no I dont know the flow rate - loads, but not a lot of pressure. I bought it second hand froma  junk shop. Buy a bigger pump than you think you need....

[rogeriko]

I install lots of irrigation systems and there are two types of pumps, high head low volume and low head high volume. What you need is the latter maybe only giving 2-3 bar pressure but delivering 6-8 cubic meters an hour.