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shadiya

Water Pressure Question

So, have been tearing my hair out, trying to design an irrigation system for the polytunnels, greenhouse and veg patch. The best pipes I can find need mains water pressure as are all pressure compensated but I want to use my rainwater harvesting system (still in the design stages too, funnily enough Wink ) as the water source, so that won't work without some sort of pump....

Now, obviously, being off grid, I don't like to chuck electricity about as I don't always have much so there has been much pencil end chewing followed by spitting out of yicky bits of flaky paint and yet still no further forward.... My life seems to be following a pattern here.... Wink Laughing

What I'd like is for someone to explain or point me at a place that explains water pressure and how to make how much, by which I mean, how high up to produce how many bars and anyway, what IS mains water pressure rated at? Shocked


If anybody has any information at all on irrigation and rainwater harvesting systems, I'd be very grateful Very Happy
Duckhead

You and me both. There was a load of that hose with little holes in on offer the other day, in Lidl. As we go downhill from the well I didn't buy any as I hadn't a clue if we had enough pressure for it to dribble out.

Hope someone answers Very Happy
Behemoth

Domestic water supply: ten metres head of pressure, at the external stop tap, at a flow of nine litres per minute. This should be sufficient to fill a one-gallon (4.5 litre) container in 30 seconds.
RichardW

You need

1 x pump
1 x pressure vessel
1 x pressure switch
1 x non return valve (if not part of the pump
Selection of plumbing fittings & pipes.

With a pressure vessel you dont need to have the pump running all the time. You can set the pressure to what the pipe needs (prob 1.5-3bar). The pump will fill the pressure vessel to the cut off pressure & then turn off. The water then slowly leaks out. Once the system pressure has dropped to the cut in pressure the pump will start up & re pressure the system.

A big pressure vessel will allow longer run times between pump activation but longer pump runs.

So the bigger the pump the larger the vessel needs to be.

We run our domestic water this way as we have no mains water.



Or you can get low pressure seepage hose or even make your own.
shadiya

Ok, you sound like you know what you're talking about, just for a change! Wink

Now when you say pressure vessel, what sort of thing could that be? I hear that it's more efficient to pump water with wind than to make electricity, so I was wondering about maybe using wind to pump the water up somewhere, thus giving me the head of pressure that I need. However, I don't have a plan for what that large high water container could actually be, all still very much early stages of thinking this through Laughing
windyridge

You need

1 x pump
1 x pressure vessel
1 x pressure switch
1 x non return valve (if not part of the pump
Selection of plumbing fittings & pipes.

With a pressure vessel you dont need to have the pump running all the time. You can set the pressure to what the pipe needs (prob 1.5-3bar). The pump will fill the pressure vessel to the cut off pressure & then turn off. The water then slowly leaks out. Once the system pressure has dropped to the cut in pressure the pump will start up & re pressure the system.

A big pressure vessel will allow longer run times between pump activation but longer pump runs.

So the bigger the pump the larger the vessel needs to be.

We run our domestic water this way as we have no mains water.



Or you can get low pressure seepage hose or even make your own.


This is very interesting.. we have mains but it takes so long to fill the kettle it is crawling out of the pipe. Do you have pressure enough to run a washing machine? Do you have central heating run off this. I am told the pressure here isnt enough to have our heating on
HenX

Knowing what your mains water pressure is like round those parts, I reckon your harvesting system will probably do better than the mains anyway!!
vegplot

A central heating pump on a timer may work as well. Just don't let it run dry so a float switch may be a useful addition.
Behemoth


This is very interesting.. we have mains but it takes so long to fill the kettle it is crawling out of the pipe. Do you have pressure enough to run a washing machine? Do you have central heating run off this. I am told the pressure here isnt enough to have our heating on


Domestic water supply: ten metres head of pressure, at the external stop tap, at a flow of nine litres per minute. This should be sufficient to fill a one-gallon (4.5 litre) container in 30 seconds.

If not please complain to your water supplier....

and your central heating should be a closed system independent of the water mains.
RichardW



Now when you say pressure vessel, what sort of thing could that be? I hear that it's more efficient to pump water with wind than to make electricity, so I was wondering about maybe using wind to pump the water up somewhere, thus giving me the head of pressure that I need. However, I don't have a plan for what that large high water container could actually be, all still very much early stages of thinking this through Laughing

For this purpose you can use the "red" type with any bladder type or even a bladderless one. You can make a lower pressure one with any container that can be mounted so that the feeder pipe is in the bottom & you can refill the upper air space as over time they do loose the stored air.

linky

For domestic use it needs to be a blue or stainless one with a EPDM bladder.

Wind pumping to a high storage would be good if you can source the pump. You will need to size the high storage to meet the full demands of the system even if you have not had any wind for a week or so.






1, Do you have pressure enough to run a washing machine?
2, Do you have central heating run off this. I am told the pressure here isnt enough to have our heating on

1, Yes
2, Not yet but we will be, but not a gas combi boiler type but it would if we had.

We have good pressure & flow, but use a 800w pump. It cycles at about 20% on time for a reasonable shower & 50% to run a bath but the garden hose needs nearer 90%.

Heating can be low pressure / vented but I am guessing you have a combi boiler & water pressure below 1 bar so you cant fill the system to working pressure. You could fit an adapter & use a garden sprayer to pump it up to pressure. Its not like it needs doing that often.


A central heating pump on a timer may work as well. Just don't let it run dry so a float switch may be a useful addition.

Heating pumps have flow but very little pressure or head. I know that they can push water round a house so you would think that it can raise water to the upper levels but as its a sealed system & the water is already in the upper pipes & rads is not actually lifting any water as the system is in balance due to the rise equalling the fall just like in a syphon.

When our last pump failed we used a new heating pump to fill the gap till the replacement arrived. We could just run the taps but the shower (not electric) would not work as the pump could not raise the water to the shower head by the 3 foot difference in height from the storage tank. The pressure switch would also not cut out as it could not get the system up to pressure so we had to turn the pump on & off as we needed water.
Ty Gwyn

What about a Ram Pump,?Double acting Rams,cannot think of the proper name

No power needed,and will lift water a hell of a way
camaro

It does chuck most of that water away past it though, only a fraction of it is "pumped". You'd need to collect that water that had been used to operate the pump and pump it to somewhere else! cassy

What about a hand pump like these for example?

We use this to supply water to the caravan; fills a 120litre tank, on a 2.4m high wooden tower which then gravity feeds the caravan.

The pump takes care of the filling side (without electricity) then you would have to have the tower the correct height to operate the hose.
shadiya

That sounds exactly like the system I have in mind for the solar shower block!
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