Drain water from 5" pipe buried 9ft underground

[druidhr]

Hello,

I'm working on my greenhouse project in my back yard.
For heating over winter I'm experimenting with earth tubing, so I buried 160ft long pipe (5" in diameter) 9ft underground. Yesterday I called friend that has camera for sewer inspection and we run on a problem. Somewhere on 80ft of pipe, we found water that is blocking airflow, water is approximately 9ft underground (on lower layer of pipe snake).

Is it possible to drain(suck) water from that pipe?

Pipe was put as snake in that trench in two levels, on image is second(upper) level, first(lower) level is same as second. There are no 90 or smaller degree turns, I did try to make turns as wider as it can be.

Thx

 

[Flyboy]

So, you’re using the air as the heat transfer medium? Because from my understanding, they usually use water or water/glycol mix as the transfer medium due to the much higher thermal mass.

 

[druidhr]

So, you’re using the air as the heat transfer medium? Because from my understanding, they usually use water or water/glycol mix as the transfer medium due to the much higher thermal mass.

Yes, air.
Requirements are not to high, just to keep greenhouse from freezing on cold day.

It is small greenhouse 260ft² and is 6ft high. Here in Croatia we don't have harsh winters. Extreme temperature lik -5C to -10C but only for day or two, and not whole day only in the morning when it's coldest. Average winter temperature is around 0-5C degrees.

 

[Baluncore]

Is it possible to drain(suck) water from that pipe?

In summer, warm air moving through the pipe will condense water as it cools. That water will pool in the pipe. In winter, cold dry air, moving through the pipe, will pick up moisture from pools in the pipe. If the pools are not there, the air returning to the greenhouse will be too dry, so the plants will be desiccated.

The only way to counter that pooling of water, is to have a gentle slope upwards along the tube, then downwards when returning to the greenhouse. That way water will, drain back to the greenhouse where it can be evaporated again. If the slope is too great, it will take more energy to blow cold air through the tube, against the thermal siphon.

Pools might be evaporated by blowing dry, chilled air into the pipe, which will pick up water as it warms. An alternative would be to slide a small diameter poly-pipe into the 5" pipe, then a pump could pull water from pools in the 5" line, out through the smaller tube.

 

[Lnewqban]

AC minisplit units have very small condensate pumps that could work full time if installed inside the duct, at the lowest point, and controlled with a water level switch.
The power wiring to the pump would have to be suitable for underground service.

 

[druidhr]

An alternative would be to slide a small diameter poly-pipe into the 5" pipe, then a pump could pull water from pools in the 5" line, out through the smaller tube.

I read a lot abut problem for pumps sucking water. It say that max height is around 20ft.

Do you think that 600W sucking pump with 3.5bar and 3000 lt/h, could suck water from that pipe?

 

[Lnewqban]

Please, see:
https://www.hvacquick.com/products/...mote-Pump-Mini-Split-Condensate-Removal-Pumps

 

[druidhr]

Please, see:
https://www.hvacquick.com/products/...mote-Pump-Mini-Split-Condensate-Removal-Pumps

I was looking in mini submersible water pumps, but none are rated to 80ft.

Maybe I'm looking it wrong.
Specs on pump you linked says that max above head is 33ft.
What does that means?
Strictly 33ft vertically or horizontal lenght is also counted?
Pipe is 9ft below ground but water is on 80ft of pipe.

 

[Lnewqban]

Vertical.
Google “pump head load”.

 

[Flyboy]

I was looking in mini submersible water pumps, but none are rated to 80ft.

Maybe I'm looking it wrong.
Specs on pump you linked says that max above head is 33ft.
What does that means?
Strictly 33ft vertically or horizontal lenght is also counted?
Pipe is 9ft below ground but water is on 80ft of pipe.

Vertical feet. Length will add a little bit of extra pressure due to friction losses, but not enough to cause issue in your case.

 

[Baluncore]

I read a lot abut problem for pumps sucking water. It say that max height is around 20ft.

I need a diagram showing the level throughout your system before I can answer that question. Pipes are usually laid with a constant slope, so they will drain by flowing downhill to an outlet. If there is a low point, called a sump, you may need to put in a vertical access pipe or a shaft. A raised portion, with a sump on either side, is called a siphon.

Let us see your diagram showing the depth levels.

 

[druidhr]

Vertical feet. Length will add a little bit of extra pressure due to friction losses, but not enough to cause issue in your case.

That's very pleasing to hear

I have Gardena sucking pump that has specified 23ft(7m) vertical sucking.

Pump specs:
Force
600 W
The largest thrust quantity
3000 l/h
Max. pressure
3.5 bar
Max independent suction
7 m
Maximum thrust height
35 m
The highest temperature of the medium
35 °C
Cable length
1.5 m
Type of power cable
H07 RNF
Level of electrical protection
IP X4

 

[druidhr]

I need a diagram showing the level throughout your system before I can answer that question. Pipes are usually laid with a constant slope, so they will drain by flowing downhill to an outlet. If there is a low point, called a sump, you may need to put in a vertical access pipe or a shaft. A raised portion, with a sump on either side, is called a siphon.

Let us see your diagram showing the depth levels.

I don't have diagram.
I can only provide image and tell you on what depth and how far from the opening of pipe is water.

On image below i marked opening on pipe where I will enter pipe. From that point, pipe goes straight to ground for 9ft and then pipe is layed like snake (like on the image).

I hope my drawing (second image) helps a bit

 

[Baluncore]

Have you filled in the hole yet?

Lay the pipe so it spirals continuously upwards from one end. The water will then flow down the spiral and collect at the lowest end, where you can reach it easily. You might install a permanent vertical pipe above the lowest point, for pulling out water when needed.

The best way to prevent frost damage in a greenhouse is to unroll an old carpet over it, so it is not exposed to the -30°C sky on clear nights. A layer of snow can do the same.
Another way is to turn on water misting units that fill the space with fog. While there is still liquid water to freeze, the temperature cannot fall below zero. You may get ice on the floor and walls, but the plants should survive.

 

[druidhr]

Have you filled in the hole yet?

Yes, and I already made greenhouse on top of it

This image is 3-4 weeks old, I already closed all openings with wooden boards (like on the right side of image) and made half of the raised beds.

 

[Baluncore]

Yes, and I already made greenhouse on top of it

OK, so feed a 1/2" or 3/4" poly-pipe into the 5" pipe, keep feeding it in until you can suck out the water. Let the small pipe remain in place for use next time.

 

[druidhr]

OK, so feed a 1/2" or 3/4" poly-pipe into the 5" pipe, keep feeding it in until you can suck out the water. Let the small pipe remain in place for use next time.

Do I need some special poly-pipe for high pressure or garden one will be good?

I found this one here in Croatia (image below), but it's only 8.5mm in diameter.

High pressure hose

Regular hose (reinforced with carbon threads)

 

[Baluncore]

I would use the black polypropylene pipe that has a solid hard wall and is used for irrigation. You will find that is slippery and sufficiently rigid, that it can be pushed into and along the 5" pipe. It comes in 100 m rolls, and will cost less than any flexible hose.

 

[druidhr]

I would use the black polypropylene pipe that has a solid hard wall and is used for irrigation. You will find that is slippery and sufficiently rigid, that it can be pushed into and along the 5" pipe. It comes in 100 m rolls, and will cost less than any flexible hose.

Thx alot for all the help

I'll come back with info after I drain water.

 

[druidhr]

I would use the black polypropylene pipe that has a solid hard wall and is used for irrigation. You will find that is slippery and sufficiently rigid, that it can be pushed into and along the 5" pipe. It comes in 100 m rolls, and will cost less than any flexible hose.

I can't find polypropylene pipe here in Croatia. Are those PPR, PEHD or PEX pipes.

 

[Baluncore]

HDPE is a possibility. High density is required, avoid LDPE or MDPE as it is too soft and flexible. Either HDPE or polypropylene is suitable.

It is very low cost and usually has green (irrigation water), or blue (potable water) stripes extruded in the black pipe wall. The pipe needs a thick hard wall, so it will not collapse when subjected to a partial vacuum, and so it can be pushed along the other pipe.
Google search for: rural green poly pipe

 

[Rive]

Can't you just somehow punch a small hole in it at the lowest point of the puddle?

 

[druidhr]

Can't you just somehow punch a small hole in it at the lowest point of the puddle?

Pipe is buried and greenhouse is on top of it.

 

[Baluncore]

Can't you just somehow punch a small hole in it at the lowest point of the puddle?

If the fan runs while the greenhouse is hotter than the ground, then some water will condense in the pipe, so the hole would need to be left open. But then the hole would allow groundwater to enter the 5" pipe. That groundwater would need to be pumped out through the smaller diameter poly pipe.

 

[sophiecentaur]

Pipe is buried and greenhouse is on top of it.

If I were you, I wouldn't want to be starting from here. IMO you need a complete re-think; there is a possible solution, though.

Water is far better than air for transporting heat. Domestic CH sometimes uses warm air but the ducts are enormous. Water will do the same job with much smaller pipes. I know the Romans used ducted hot air from fires but their whole system was designed from the start to cope with condensation. (I bet there were problems with monoxide poisoning with some of their systems.)

What are you using as your source of hot air at present? Why did you bury the pipes so deep? Domestic under-floor heating is only just below floor level and there is less wasted heat. If you were planning to dig the soil in the greenhouse you would need some extra depth.

Air locks and 'water locks' are always a potential problem but, if you have a gentle constant slope a good blast with mains pressure water would clear air locks.

I can only suggest that you leave those pipes where they are and lay new pipes horizontally (or with a small constant slope. Pump warm water in a direction up-hill and small bubbles will be swept away to the outlet.

 

[Baluncore]

I think this is a practical learning exercise.

Removing heat from the earth below the greenhouse in winter, and transferring that to the air in the greenhouse, will cool the floor of the greenhouse. To counter that, you should heat the earth deep below the greenhouse in summer, by circulating hot air from the greenhouse, back through the pipe, storing the heat for winter, underground. That summer cycle will condense water in the deep pipe, which will form another water-lock.

Is the 5" pipe rated for 15 psi external pressure? It may collapse under the hydrostatic pressure of wet soil, 9 feet below the greenhouse.

 

[druidhr]

Water is far better than air for transporting heat. Domestic CH sometimes uses warm air but the ducts are enormous. Water will do the same job with much smaller pipes.

I know that, I have under-floor heating in my house, and of course it is much better but it is much more expensive.

What are you using as your source of hot air at present? Why did you bury the pipes so deep? Domestic under-floor heating is only just below floor level and there is less wasted heat. If you were planning to dig the soil in the greenhouse you would need some extra depth.

Google "earth tubing".

@Baluncore partially explained it.

 

[druidhr]

To counter that, you should heat the earth deep below the greenhouse in summer, by circulating hot air from the greenhouse, back through the pipe, storing the heat for winter, underground. That summer cycle will condense water in the deep pipe, which will form another water-lock.

Logic is good, but storing energy in earth is for short term. I attached pdf file that explained termal saturation and recovery.

Is the 5" pipe rated for 15 psi external pressure? It may collapse under the hydrostatic pressure of wet soil, 9 feet below the greenhouse.

Yea, I bought special double wall couagurated pipe that are designed to be buried directly into the ground. They have wide range of applications, here in Croatia optical fibre cables are pulled through (you know optical cables are very sensitive lateral bending)

 

[sophiecentaur]

I know that, I have under-floor heating in my house,

I get the message now - 'free' heat when you want it is always good news.
Would you expect your under floor heating to work as well with air in the pipes?
The heat below your greenhouse will be stored in the soil down there and also in whatever is in the pipes. Where is the advantage of air?* The specific heat capacity of liquid water is by far the highest of commonly available materials and that makes it attractive in most applications. There would be several methods to take surplus heat from the greenhouse; some cheap steel radiators on the shady side of the green house could be connected to your existing pipework. A small pump could circulate the water, controlled by a very basic thermostat, which would turn on the pump when the air temperature in the greenhouse is too warm or too cold. No need to change direction of pump.
This is a very difficult project to get 'right' because the devil is in the detail. Did you, by any chance , bury a thermometer at the bottom of the hole? What sort of temperature difference would you expect between the greenhouse air and the bottom of the pit? And what temperature difference would you expect, on a very hot (or cold) day, between the air going in and the air coming out?

*I can see just one advantage of using air and that is the system doesn't contain a heat exchanger at the top.

 

[druidhr]

Would you expect your under floor heating to work as well with air in the pipes?

No, earth tubing with air is less effective.

Did you, by any chance , bury a thermometer at the bottom of the hole?

No I didn't not.

What sort of temperature difference would you expect between the greenhouse air and the bottom of the pit? And what temperature difference would you expect, on a very hot (or cold) day, between the air going in and the air coming out?

Requirements are not to high, just to keep greenhouse from freezing on cold day.

It is small greenhouse 260ft² and is 6ft high. Here in Croatia we don't have harsh winters. Extreme temperature lik -5C to -10C but only for day or two, and not whole day only in the morning when it's coldest. Average winter temperature is around 0-5C degrees.

 

[sophiecentaur]

No, earth tubing with air is less effective.

So why choose air? Cheaper and less trouble, of course but a 'heat exchanger' of some kind at the top would help get better results.
I was browsing through Amazon to get some background knowledge about greenhouse heaters. They start at about 60W and go up to around 200W so that's the equivalent of power you'd be needing (I assume). I also assume that the greenhouse is draught proof. The roof looks as though it's insulated

I re-read your posts and you mention 'raised beds'. If you used a water system, you could run hoses in the soil in the beds. Warm (not freezing) soil is always good for starting off plants and your heat would be going where it's needed most. But that could complicate things because you would be better by getting the heat not from the beds so your control system would need electric valves (fairly cheap in plumbing stores.) to bring your heat absorbing CH radiators into play.

At this point people tend to start suggesting Raspberry Pie processors for controlling the system. But you may not be into that stuff.

Possible experiment would be to use a small fan, blowing down your pipe and see the temperature difference between input air and exit air. ( very low power laptop cooling fan)

 

[druidhr]

So why choose air? Cheaper and less trouble, of course but a 'heat exchanger' of some kind at the top would help get better results.

Isn't that enough to go for another solution?

But thx for all the suggestions, earth tubing with water for heat extracting is very good solution. Will think about it for my next project.

 

[sophiecentaur]

Isn't that enough to go for another solution?

But thx for all the suggestions, earth tubing with water for heat extracting is very good solution. Will think about it for my next project.

I'd be tempted to go for a water-based solution for the reasons I've given but, if you do some measurements - even just to feel a difference in the air that comes out - and if it 'feels right' then use air. You can always change to water if this winter's experience is not satisfactory.

Maybe your raised beds should have some insulation underneath.Enjoy your out of season veg!

 

[druidhr]

You can always change to water if this winter's experience is not satisfactory.

Yes, if air fails as heat extractor, I could pull 1/2" HDPE pipe through 5" pipe and fill it with water.

 

[sophiecentaur]

Yes, if air fails as heat extractor, I could pull 1/2" HDPE pipe through 5" pipe and fill it with water.

It should be worth while filling the outer pipe with water - both for good thermal contact with where the heat is transferred from and to and for thermal capacity. On that topic, if you want good heat transfer on hot days, you would benefit from a number of heat exchangers above ground. That would make the best of any available heat and reduce unwanted leakage at night. I mean a sort of thermal ratchet. A simple (CH ) pump could control heat transfer by using a thermostat.
A greenhouse already needs some way to avoid overheating so radiators (the pump) could be switched on before the windows / vents are opened..

You really need a thermometer (or several) for this to allow you to get best performance or at least to convince yourself that the system is working. Shame they are soo expensive!