airtight cold water storage tank overflow?

slipstream

hiya,

we are building a dormer bungalow at the moment and trying to maximize air-tightness.

we have two storage tanks in the over eaves area (mains and rainwater).

we had planned to put hepvo valves on both overflow pipes to prevent air getting in but the plumber is concerned that they might restrict the overflows and lead to flooding.

what do you guys think?

also, what alternative do you think would make most sense?

thanks for your help,

slip

freddyuk

Install Hepvo in a vertical drop from cistern and then out to the eaves? Would plumber accept that? They are designed for gravity flow so the more water the more they will open up to maximum circumference.

slipstream

freddyuk wrote: »

Install Hepvo in a vertical drop from cistern and then out to the eaves? Would plumber accept that? They are designed for gravity flow so the more water the more they will open up to maximum circumference.

Thanks Freddy. The plumber was worried that the valve would either not open or not allow sufficient flow at the critical moment when it is needed.

A further issue is that the current overflow pipe is 3/4 inch and the hepvos are 1 1/4 or 1 1/2 inch.

If the hepvo would not be completely reliable then would two overflows be an option, a lower one via the hepvo to the soffit and a higher one to drains?

Slip

freddyuk

It is not a "valve" as such. It is a plastic/fabric tube which is flattened so is closed at the end. Thus no air can blow up the pipe. Any water flowing down just pushes it's way through the tube and the more water the more it is pushed open. Then it just self closes again. There is nothing mechanical holding this closed so nothing to fail - it is a clever idea. It was never designed for overflows so not sure smaller then 1.25" is available.

Alucan

If you bring the overflow out of the tank below the water level then raise the pipe to drain off level the water will create a barrier. Think of the trap under your sink it works in the same way

freddyuk

There is a danger of very cold air blowing up the pipe in winter and freezing a small amount of water in a trap thus blocking the overflow? I know it's unlikely but then so is getting Legionella but everyone has to have that setting option on their system. No water means no danger of blockages.

slipstream

so would you guys trust a hepvo valve on an overflow?

also would you install it horizontally or vertically and close to the tank of close to the eaves?

slip

Wearb

Put a trap on it and fill it with cheap alcohol or some other non poisonous antifreeze.

corkgsxr

I wouldn't trust them myself Iv seen them go hard and stop opening.

K.Flyer

slipstream wrote: »

so would you guys trust a hepvo valve on an overflow?

also would you install it horizontally or vertically and close to the tank of close to the eaves?

slip

I wouldn't.
I would prefer to have no restrictions and as few bends as possible on an overflow warning pipe so as the water can get out fast without any problems.
Is having this small pipe open really going to make any difference considering that it's most likely going to be in the attic?

slipstream

K.Flyer wrote: »

I wouldn't.
I would prefer to have no restrictions and as few bends as possible on an overflow warning pipe so as the water can get out fast without any problems.
Is having this small pipe open really going to make any difference considering that it's most likely going to be in the attic?

The total air leakage at present represented in 2d is about half of an a4 page so those two holes would be fairly significant.

How about a deep u bend on the overflow? I don't think the water would freeze would freeze as the storage tank is in a heated space.

Wearb

slipstream wrote: »

How about a deep u bend on the overflow? I don't think the water would freeze would freeze as the storage tank is in a heated space.

How about dropping a pipe down a bit below the surface of the water in the tank. You could fit anti syphoning device, but I don't see necessity for it.

slipstream

Wearb wrote: »

How about dropping a pipe down a bit below the surface of the water in the tank. You could fit anti syphoning device, but I don't see necessity for it.

Just so I understand, would the overflow pipe rise to the required overflow level before dropping down to to the soffit?

Wearb

slipstream wrote: »

Just so I understand, would the overflow pipe rise to the required overflow level before dropping down to to the soffit?

I don't understand your question. What required rise are you asking about.

slipstream

Wearb wrote: »

I don't understand your question. What required rise are you asking about.

Sorry, I thought you were suggesting that the overflow inlet would be below the usual water level to create an airtight seal but I guess this would mean constant overflows unless the pipe then rose up to the level you wanted the overflow to be activated at.

Apologies if I am not being clear.

K.Flyer

The overflow pipe would be connected to the tank in the normal way, at the normal position, except that from the inside of the connection there would be a down ward angled piece of pipe which would be cut below the water line.

Wearb

slipstream wrote: »

Sorry, I thought you were suggesting that the overflow inlet be below the usual water level to create an airtight seal but I guess this would mean constant overflows unless the pure then rose up to the level you wanted the overflow to be activated at.

Apologies if I am not being clear.

Got you. The usual outlet would be a few inches above normal water level and the overflow pipe would drop all the way to the gutter or similar.
I was suggesting that the outlet (uptake) at tank side be dropped down a couple of inches into the water.
The overflow would not take water until the water reached the level of the outlet flange in the tank, but (without an anti syphoning device) would continue until water dropped below level of extension into water tank.

slipstream

Wearb wrote: »

Got you. The usual outlet would be a few inches above normal water level and the overflow pipe would drop all the way to the gutter or similar.
I was suggesting that the outlet (uptake) at tank side be dropped down a couple of inches into the water.
The overflow would not take water until the water reached the level of the outlet flange in the tank, but (without an anti syphoning device) would continue until water dropped below level of extension into water tank.

that sounds a great idea.

would you attach a 90 degree joint to the tank side of the outlet flange and then add some pipe so that the uptake was below the usual water level? and can you get 90 degree joints for 3/4" pipe?

have you seen this done before?

thanks,

slip

Wearb

I would use an Instantor 316 inside the tank with a short pipe dipping down into the water and a 312 outside. There may be better fittings nowadays. It's a long time ago since I did any great amount of plumbing. The plumbers here may know of better fittings.
No I haven't seen it done.

slipstream

Wearb wrote: »

I would use an Instantor 316 inside the tank with a short pipe dipping down into the water and a 312 outside. There may be better fittings nowadays. It's a long time ago since I did any great amount of plumbing. The plumbers here may know of better fittings.
No I haven't seen it done.

I guess if the tank was overflowing then the output could be greater due to siphonage (depending on the overflow pipe length inside the tank from flange to uptake).

Can you foresee any risks or potential issues with this setup?

Thanks for all the help as this should hopefully save me a lot of grief.

Slip

K.Flyer

I have seen it done before, a lot of the combination hot / cold water cylinders fitted to apartments in Dublin were pre-assembled like this and it works perfectly fine and so there should be no issues in setting up the pipe-work in this way.
The connections that you need will be available from any plumbing supplies outlet.

Wearb

slipstream wrote: »

I guess if the tank was overflowing then the output could be greater due to siphonage (depending on the overflow pipe length inside the tank from flange to uptake).

Can you foresee any risks or potential issues with this setup?

Thanks for all the help as this should hopefully save me a lot of grief.

Slip

I don't think that there is any need for anti syphon valve. The overflow should be sized to be able to at least take the flow from the fill pipe.
So I don't see any problem, so long as there isn't a sag in the overflow pipe that could allow for water to lie and freeze. Mind you that would be a condition of any overflow pipe.