How to make Attic cold water tank Airtight

delfagio

Hi all,

The overflow pipe in the attic cold water storage tank is currently an open end inside the tank ready to take water if the tank ever overfilled.

Question is how can I make this pipe airtight. I though of putting a 90bend and a short section of pipe down and into the water tank below the water level, but would this cause siphoning and suck water out of the tank.

How is this normally done in houses these days

Thanks all

filbert the fox

delfagio wrote: »

Hi all,

The overflow pipe in the attic cold water storage tank is currently an open end inside the tank ready to take water if the tank ever overfilled.

Question is how can I make this pipe airtight. I though of putting a 90bend and a short section of pipe down and into the water tank below the water level, but would this cause siphoning and suck water out of the tank.

How is this normally done in houses these days

Thanks all

now I'm really confused! What do you mean inside the tank? does the overflow not discharge to outside for observation should the tank overflow? What ultimately are you trying to do when you refer to airtightness?

delfagio

filbert the fox wrote:

now I'm really confused! What do you mean inside the tank? does the overflow not discharge to outside for observation should the tank overflow? What ultimately are you trying to do when you refer to airtightness?

Yes the overflow pipe discharges to the outside, that's not issue here.

I'm talking about the end of the over flow pipe that's on the inside of the storage tank. Air is free to blow in through this pipe from the outside of the house. I want to stop this. That's what I mean by airtightness.

Metric Tensor

In many cases the cold water tank is outside the air tightness envelope. Either up in the attic or in an unheated side attic.

Where is yours located with respect to your AT envelope OP?

P.S. Some sort of non return or one way valve might do the job.

Calahonda52

How to make Attic cold water tank Airtight?

You don't, because the science says if you make it 100% airtight, the cold water wont leave the tank as nature abhors a vacuum.

if you look closely here,
http://ie.tricel.eu/cold-water-storage-tanks/one-piece-tanks/
you will see a vent hole on the top, which is fitted with a cowl that lets air in and out but stops crap getting in and mice using it as an Olympic pool.

AS MT has pointed out if the tank is outside the A/T layer then no worries, cold air in the overflow and maybe some out the vent.
If inside the A/T layer then you could consider extending the top vent back out through the A/T layer, as the over flow will usually be out through it.
As Foxy has said, you do need to be able to see it, and ideally it should have no mechanic devices on it that might stick, because in an ideal world, it should never be used

delfagio

Metric Tensor wrote:

Where is yours located with respect to your AT envelope OP?

Thanks Metric

Yes the cold storage water tanks are in my attic but the entire attic is within the AT envelope of the house. It's all made of the SIP panels.

Johnnyhpipe

Surely this only creates a vaccum and restricts the flow of water - like dipping a straw into your drink and putting your finger on top..?

I wouldn't be so concerned about air getting in through this pipe..its hardly going to make a noticeable difference. But if you're that concerned then internal baffles or a non return valva would seem a reasonable solution.

Metric Tensor

If you only turn the pipe down a short distance below the top water level then even if siphoning did occur (which could only happen directly after an extreme overflow case or in theory with a VERY high wind) the siphoning would immediately stop once the water dipped below the inlet level.

The tank would then return to normal operation.

You can't siphon if there's no submersion on the inlet end.

Calahonda52

delfagio wrote: »

Thanks Metric

Yes the cold storage water tanks are in my attic but the entire attic is within the AT envelope of the house. It's all made of the SIP panels.

Where is the cold feed coming through the A/T layer into tank?

Water John

Put a Duck Valve on the outside if you are concerned about it.

Metric Tensor

Water John wrote: »

Put a Duck Valve on the outside if you are concerned about it.

The simple solutions are the best ones. Great idea Water John

Water John

Yeah metric, I know I'm simple.

delfagio

Cheers guys, I'll look into a non return valve of some sort, that is probably the easiest solution.

K.Flyer

You should not fit a non-return valve of any sort on the overflow warning pipe in case it gets stuck in the closed position. If this was to happen and you had a complete failure of the ball-cock you could very easily have a flood situation.
The most simple and effective way is to extend the overflow warning pipe to a few inches below the water line.
This will retain your airtight seal, but also has the additional effect of possibly syphoning water from the tank to remove water quicker in the event of ball-cock failure.

delfagio

K.Flyer wrote:

You should not fit a non-return valve of any sort on the overflow warning pipe in case it gets stuck in the closed position. If this was to happen and you had a complete failure of the ball-cock you could very easily have a flood situation. The most simple and effective way is to extend the overflow warning pipe to a few inches below the water line. This will retain your airtight seal, but also has the additional effect of possibly syphoning water from the tank to remove water quicker in the event of ball-cock failure.

Thanks K.Flyer,

I'll revert back to my original idea so and see how it works out.