# Unvented water heater regulations



## Russell RA Tech (Nov 27, 2014)

Hi Guys

In the UK we have the regulations that governs all installations for unvented cylinders over 15litres they are called G3 water regulations.
Our building regulations also cross over in the same manner and they are found under sections G (again but confusingly) and H.

Specifically I am interested in the regulations concerning the discharge from the PRV. Generally in the UK it is a regulation that the water discharged must do so "safely and in a conspicuous manner" That results in utilizing a tundish and then running to outside or a foul soil or waste pipe via some mechanical (i.e. non wet) device.

Do you have similar circumstances in the US and if so what do you normally do?

Thanks for allowing me to be on your forums.

regards

Russ


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## plbgbiz (Aug 27, 2010)

By "tundish" I am assuming you mean what is pictured in this diagram.

We have those here also. But usually we only see them on the drain outlet of a Reduced Pressure Zone (RPZ) backflow prevention device and they are referred to as Air Gap Fittings. Here is a link to the PZ member Flyout95's post showing one of his installs.

I don't think I have ever seen one used on a domestic water heater. Boiler maybe, but not a residential unit.

Our pressure relief drains still have to have an air gap, we just don't have a specific fitting for it. Maybe we should.


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## dhal22 (Jul 30, 2010)

plbgbiz said:


> By "tundish" I am assuming you mean what is pictured in this diagram.
> 
> We have those here also. But usually we only see them on the drain outlet of a Reduced Pressure Zone (RPZ) backflow prevention device and they are referred to as Air Gap Fittings. Here is a link to the PZ member Flyout95's post showing one of his installs.
> 
> ...



Very well written, concise explanation. Before I realized what the OP was asking you had it rewritten in USA terminology.


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## Russell RA Tech (Nov 27, 2014)

Hi Plbgbiz

This is a uk standard "tundish" http://www.advancedwater.co.uk/prod...B0Ry-KAKhaR8p86zM8HLixw8H5cinz8eWURoCICDw_wcB

And yes what is shown on the RPZ I would consider a tundish.

In the UK it is not allowed to "hard pipe" from the PRV directly to a foul waste or soil pipe, it has to have a "safe and conspicuous method of discharge" It is therefore acceptable to have a tundish fitted

This does two things

1/ Allows the user to see that either the PRV is letting by, indicating that there is a problem with the cylinder (i.e. a method of warning) or there is a problem with PRV itself
2/ Prevent undue consumption because you can see that water is passing

If your domestic cylinders don't have this how do you know something is wrong? Unless you can just run a pipe over a local open trapped gully

Thanks for responding

regards

Russell


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## Russell RA Tech (Nov 27, 2014)

dhal22 said:


> Very well written, concise explanation. Before I realized what the OP was asking you had it rewritten in USA terminology.


 It's a learning curve for me, translation from UK to USA terminology. 

Please bear with my poor knowledge of your USA terms - I'll get there!

Having said that it always interesting to know that we speak the same language (English) but have evolved differing terminologies

Russ


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## plbgbiz (Aug 27, 2010)

Russell RA Tech said:


> ....1/ Allows the user to see that either the PRV is letting by, indicating that there is a problem with the cylinder (i.e. a method of warning) or there is a problem with PRV itself
> 2/ Prevent undue consumption because you can see that water is passing
> 
> If your domestic cylinders don't have this how do you know something is wrong? Unless you can just run a pipe over a local open trapped gully
> ...


Add to that:

3/ Prevent contamination of the potable drinking water from a backup of soil or foul water.


Basically, you are doing the same thing we do and for the same reasons. Protect the potable water supply and be sure someone sees it so the water heater or relief valve can be repaired (and kept safe).

The relief drain on our residential water heaters (cylinders) are required to have a temperature and pressure relief valve with a drain no matter what size or what use they are intended. That drain must have an air gap.

Our local codes and inspectors allow a variety of air gap designs as long as the function is accomplished.


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## plbgbiz (Aug 27, 2010)

Russell RA Tech said:


> ...Please bear with my poor knowledge of your USA terms - I'll get there!...


No problem old chap. We ain't exactly masters of the Queen's English either.


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## Russell RA Tech (Nov 27, 2014)

Cheers plbgbiz

yes I agree with 3/ we call it a tundish with break to drain. 

The tundish itself has some quite stringent dimensions it has to conform to here. Our regulators determine it suitability with a standard called "test Code 2" (don't know why) and you then have to run the outlet either to outside or, via a mechanical trap (to prevent smells), to a local foul waste or soil pipe.

I'll try and attach the standard requirements at the moment it is 104kb and I cant upload it as the limit is 100kb 

Russ


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## Russell RA Tech (Nov 27, 2014)

plbgbiz said:


> No problem old chap. We ain't exactly masters of the Queen's English either.


OOOH how did you know I was old?

Did my picture give it away? lol

Russ


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## Ghostmaker (Jan 12, 2013)

*608.14.2.1 Relief port piping*. The termination of the piping from the relief port or air gap fitting of a backflow preventer shall discharge to an approved indirect waste receptor or to the outdoors where it will not cause damage or create a nuisance.

The tundish provides an air gap. Basically depending on the size of the water main the indirect waste receptor (floor drain) in my state must be sized to handle a check number 1 failure. The other alternative is pipe it to the exterior of the building.


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## Russell RA Tech (Nov 27, 2014)

Hi ghost

Thank you. That's the type of info I was looking for

I can't seem to locate the relevant U.S. regulations on Google

Can you tell me what they are called in the states? Over here we have the water regulations and they are found under the sub code of "G3 unvented water heaters" also related are the building regulations under "approved document(s) G & H!

But we are allowed to discharge via a tundish to a mechanical device (not a wet trap) and then to a waste or soil pipe (provided it can handle the temp)

Could you guys use a mechanical method of preventing smell coming back from the drain 

I could post pictures of our devices if you want or would like to see our alternatives?

Cheers

Russ


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## BC73RS (Jan 25, 2014)

In Canada we use approved trap primers.


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## BC73RS (Jan 25, 2014)

I don't understand the 'not a wet trap" part, maybe you mean a backwater valve in the drainage system to prevent sewer gas?


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## Russell RA Tech (Nov 27, 2014)

Say there was such a thing as a tundish with its own inbuilt one way odour seal. After the tundish you can then run hard pipe to a soul or waste pipe


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