Can Evac Tubes Gravity Feed?

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Re: Can Evac Tubes Gravity Feed?

Postby jimbo » Mon Feb 18, 2013 10:24 pm

We ran out of BBQ gas over new year so we just dragged the 45kg out and used that. Surprised how little we have used in 6 months.
The previous owners ( family of 4) have recorded their gas usage and over summer they got similar results but in winter went through a 45kg every 2 or so months however we don't have a wet back. I would really like to add one to the system as we will probably have the heater running for 6 months of the year.....we like a toasty house! Our problem is that we have a standard pressure storage tank under the house. Not sure if it can still be done.
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Re: Can Evac Tubes Gravity Feed?

Postby Paddy360 » Wed Feb 20, 2013 8:44 pm

If you are off the grid the tank stand is the best solution by far. Take a drive out around some old homesteads that began long before the grid was even thought of and they all had tanks on a stand. Pump playing up? No hassles, you do have time to repair it. What about a petrol powered pump? Big tank, fill it once a week?
A large expansion tank may sound good in terms of reducing the number of starts in the hour for your pump but at the end of the day wether you pump it now or later, you are still going to pay to pump it. Going from no tank to say a 100L tank might save you at best 30% on your pump costs. Given the cost of a 500L expansion tank and the fact that most exp tanks wont last 8 years starts to eat into your 30% saving.
I believe Grundfos have a domestic constant pressure pump that claims to be super efficient. Possibly inverter driven. Just be wary of very low water flow rates which can burn these variable speed pumps out. Best of luck building that tank stand at the weekend!
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Re: Can Evac Tubes Gravity Feed?

Postby Cherokee Solar » Thu Feb 21, 2013 8:15 am

Shebee wrote:Gordon, the 500 litre tank is the pump connected, diaphram type. I think it might be a better option for me than a tall tank stand.


Hi Shebee,

There is no such thing as a free lunch! :D

Whatever system you choose to install, they will all consume energy. I use a small pressure tank here for the household water and it too takes energy to keep this tank pressurised. The pump may not cycle as much, but each time it does, the pump will operate for longer periods of time than if no pressure tank was installed.

In fact, you could argue that using a very large pressure tank such as the one you are discussing will actually use more energy to keep the tank pressurised because of the inherent losses of pressure over time.

The old timers used to use a low volume wind driven pump to move the water up to a high level tank (ie. tank on a stand) where it would be available for later use within the household.

If there was a simple, low cost, energy efficient method of moving water about the place at pressure in an off the grid household, we'd all be using it. Unfortunately, the normal household pressure pump is probably about the most energy efficient, low cost, method of achieving this.

Shebee wrote:avoiding all the high-energy-use start ups everytime


I haven't noticed that the pumps have a high energy use start up. The energy drawn by the pump is fairly constant but does tail off a little bit towards the end of the cycle.

I reckon the most energy efficient method would be to use a small good quality DC pump with a solar panel and a pump maximiser (avoids the battery) and pump the water to a high level tank for only a few hours per day.
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Re: Can Evac Tubes Gravity Feed?

Postby Shebee » Thu Feb 21, 2013 4:37 pm

I hope this post works. I have submitted a few that haven't shown up.

Yep, free lunches are rare and wasn't expecting one with moving water around, just trying to find the best option for us.
I have a friend who has a few times over the years had to clean out their header tank on a stand. They have climbed the 10metres up to the tank and then into it to clean it out. That is something I am just not going to be able to do.

As for the pressure pumps, the two that I've had used more than twice their running power to start up, before settling into constant pumping. To have a pump run constantly 3 times a day has got to save power on potentially 100 start ups per day. I guess I'm needing to weigh up the pros and cons.

SO, for those of you who have tanks on towers, or up hills, how high are they from house ground level?
Gordon says his is 25 metres up the hill. What height would be needed to get some decent pressure into the house?

Thanks again :D
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Re: Can Evac Tubes Gravity Feed?

Postby Gordon-Loomberah » Thu Feb 21, 2013 6:06 pm

If you only put clean water into the tank, and keep the water in the dark (keep the cover on), it should be decades before it needs cleaning. I've certainly never had to clean out a big steel tank thats been on my shed for over 15 years.

Country people have successfully lived with gravity fed showers from hot water tanks in the roof space, ie a pressure head of only a couple of metres. It works much, much better if hot and cold are at the same pressure!

However, while it will work for a shower head with large holes, or filling a bath or sink, that sort of pressure is pretty hopeless when trying to water the garden, the water pressure is just too low.

If you use a DC pump, the start-up current is much lower than typical AC motors, and they are a lot more efficient too. I used a small Johnson pump designed for hosing down boats etc for a few years to pump up to my 25m head tank.
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Re: Can Evac Tubes Gravity Feed?

Postby Shebee » Fri Feb 22, 2013 3:48 pm

Just priced a 15m tank stand $8,408 NOT including delivery, installation or the tank on top :o :shock: :( !
Mmm, that $1900 pressure tank is looking good again.

Will get some more quotes, but it isn't looking good so far :|

On the topic of DC pumps, are there any pressure pumps that provided enough water for general household use? When I've google searched I haven't found anything that delivers more than 20 litres per minute and I'm assuming you'd want more than that for your house, being pumped directly,
To fill a tank would be fine though (if you can afford a big stand to go with it :( , or have a big hill ;) ) or maybe to fill a pressurised tank? Or would there need to be more pressure from the incoming water to properly pressurise it?

Have just found out that roof trusses being delivered next week are not strong enough to hold a HWS tank ON the roof. They have been designed to take the tank IN the roof.

This off-grid owner building thing makes my head hurt, next time I am bored and need a project I might just get a job :lol: but don't you dare tell my husband that :lol: .
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Re: Can Evac Tubes Gravity Feed?

Postby Cherokee Solar » Sat Feb 23, 2013 10:25 am

Hi Shebee,

Shebee wrote:Just priced a 15m tank stand $8,408 NOT including delivery, installation or the tank on top


Yeah, the old timers generally would have made their own tank stands.

Shebee wrote:I haven't found anything that delivers more than 20 litres per minute and I'm assuming you'd want more than that for your house, being pumped directly


I think normal house pressure is only about 15 litres per minute. I have a 12v Shurflo DC pump that provides 11 litres per minute and it is only slightly less than normal household pressure. It is very efficient, although I would want a bit more pressure than that on a household pump to run the fire sprinklers.
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Re: Can Evac Tubes Gravity Feed?

Postby Cherokee Solar » Sat Feb 23, 2013 10:28 am

Shebee wrote:This off-grid owner building thing makes my head hurt, next time I am bored and need a project I might just get a job :lol: but don't you dare tell my husband that :lol: .


Good one. I owner built my house here doing most of the work myself with my lady, except for excavations, plumbing and 240v electrical, so if you need any advice set up a new thread on the forum and ask away.

Chris
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Re: Can Evac Tubes Gravity Feed?

Postby Gordon-Loomberah » Sat Feb 23, 2013 11:36 am

Shebee wrote:Just priced a 15m tank stand $8,408 NOT including delivery, installation or the tank on top :o :shock: :( !


If you are handy with a welder, or know someone that is, you could easily build a 3 or 4m high stand strong enough for a 2 or 3000l tank for under $1000.
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Re: Can Evac Tubes Gravity Feed?

Postby Shebee » Sun Feb 24, 2013 6:06 am

Thanks Chris, for your replies. No doubt I'll have many questions along the way :D !

Gordon, our HSW tank will be about 5.5metres off the ground so the tank would need to be taller than that to gravity feed to it. I was under the impression a tank would need to be 15m or so high to supply enough pressure to the house? I need to find out head height, pipe size, etc for the presure don't I? I think a trip to the irrigation store might be istall!
Yes, we do know a very experienced welder. We are hoping to get him to build our ground mounted PV frame. I might just see if we can add a tank stand to the list :D

Thanks again for the replies!
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