Vented DHW tank. Can I change to unvented?

deravarra

Hi all.

I have an unvented DHW tank. Can I change it to an unvented one?

I see one advantage in going for unvented - better pressure throughout the house. But what, if any, disadvantages would there be?
How difficult would it be?
And what would it be likely to cost?

Lenar3556

deravarra wrote: »

Hi all.

I have an unvented DHW tank. Can I change it to an unvented one?

I see one advantage in going for unvented - better pressure throughout the house. But what, if any, disadvantages would there be?
How difficult would it be?
And what would it be likely to cost?

You could if it’s not heated by solid fuel. But they are not cheap, and really you are looking at installing a water storage tank and 3 bar pump upstream of it.
Mains supply is unlikely to be sufficient on its own.

If poor pressure is your issue, I would be looking at fitting a booster pump on the outgoing of your existing cylinder.

Car99

deravarra wrote: »

Hi all.

I have an unvented DHW tank. Can I change it to an unvented one?

I see one advantage in going for unvented - better pressure throughout the house. But what, if any, disadvantages would there be?
How difficult would it be?
And what would it be likely to cost?

300L invented triple coil tank is about €800. You may not need three coils now but if you add solar or similar at a later date it's better to have it in there . Labour plus hardware is dependant on location current pipework condition and accessibility.

K.Flyer

deravarra wrote: »

Hi all.

I have an unvented DHW tank. Can I change it to an unvented one?

If your question is can you convert your existing cylinder to be unvented, the answer is No.

deravarra wrote: »

I see one advantage in going for unvented - better pressure throughout the house.

As already mentioned, only if you install a decent booster pump supplied with water from the attic tank.
You are not supposed to connect anything other than the kitchen cold tap and a cold water storage tank to the incoming mains water supply.

deravarra wrote: »

But what, if any, disadvantages would there be?
How difficult would it be?

They must be installed correctly, especially with regards to safety pressure relief valve discharge pipework. A lot are not done properly and cause problems.
You may have noise from the pump.
Cost.

deravarra wrote: »

And what would it be likely to cost?

If done correctly, probably a lot more than you would expect.

Why not get a good quality 3bar water pressure boosting pump and just increase the water pressure that way?

deravarra

K.Flyer wrote: »

If your question is can you convert your existing cylinder to be unvented, the answer is No.



As already mentioned, only if you install a decent booster pump supplied with water from the attic tank.
You are not supposed to connect anything other than the kitchen cold tap and a cold water storage tank to the incoming mains water supply.



They must be installed correctly, especially with regards to safety pressure relief valve discharge pipework. A lot are not done properly and cause problems.
You may have noise from the pump.
Cost.



If done correctly, probably a lot more than you would expect.

Why not get a good quality 3bar water pressure boosting pump and just increase the water pressure that way?

I wasnt looking to convert the current cylinder. I was wondering more about changing to an unvented, as this would remove the need for a pump as the pressure would be sufficient from an unvented system to provide for a decent shower.

As for the suggestion that nothing apart from kitchen water or attic tank should be connected to mains water - I am not convinced of that. Thats why we have unvented cylinders.

However, I think perhaps the pump might be the better way to go as it would be a lot easier.

K.Flyer

deravarra wrote: »

I wasnt looking to convert the current cylinder. I was wondering more about changing to an unvented, as this would remove the need for a pump as the pressure would be sufficient from an unvented system to provide for a decent shower.

As for the suggestion that nothing apart from kitchen water or attic tank should be connected to mains water - I am not convinced of that. Thats why we have unvented cylinders.

However, I think perhaps the pump might be the better way to go as it would be a lot easier.

Where are you getting the idea that by just putting in an unvented cylinder by itself will automatically give you extra pressure.
Look up Irish water and building regulations regarding what can and can't be connected to mains water, that might convince you.
As for the "..that's why we have unvented cylinders" comment, that makes no sense at all. I could install a 3 bar dual impeller pump on a standard domestic system and it could produce a much better result than an unvented cylinder connected directly to the mains supply.
Every apartment that I have worked in with unvented cylinders as standard are not mains fed. They are fed from a central high pressure pumped system taking water from a storage tank.
Any I have installed have allways had the water supply taken from water storage tanks via a suitable pump with very satisfactory results.
Also, the amount of incorrectly installed unvented cylinders retro fitted into houses is shocking, often leaving home owners with water damage and extra costs to rectify the errors.

deravarra

K.Flyer wrote: »

Where are you getting the idea that by just putting in an unvented cylinder by itself will automatically give you extra pressure.
Look up Irish water and building regulations regarding what can and can't be connected to mains water, that might convince you.
As for the "..that's why we have unvented cylinders" comment, that makes no sense at all. I could install a 3 bar dual impeller pump on a standard domestic system and it could produce a much better result than an unvented cylinder connected directly to the mains supply.
Every apartment that I have worked in with unvented cylinders as standard are not mains fed. They are fed from a central high pressure pumped system taking water from a storage tank.
Any I have installed have allways had the water supply taken from water storage tanks via a suitable pump with very satisfactory results.
Also, the amount of incorrectly installed unvented cylinders retro fitted into houses is shocking, often leaving home owners with water damage and extra costs to rectify the errors.

Rather than berate and belittle, I would have expected a little help.

For someone like myself who is not a professional to be asking advice to come across someone like yourself with the answers you give in the manner you give them is quite offputting.

Would you agree that an unvented system - which would be a replacement for a vented system - gives far more pressure than a vented system?

My information was gleaned from a few websites.

In one water cyclinder manufacturer's website, I saw the following:

A traditional vented cylinder requires connection to a water tank, usually in a loft or attic space, using gravity to deliver hot water to the home. ... An unvented cylinder uses a pressurised system, that has a direct feed from your cold water supply, so there is no need for a cold water storage tank in the loft or attic.

That itself would suggest that IT IS possible to connect the mains water. Perhaps you could take up the Irish water and building regs with them.

The "thats why we have unvented cylinders" comment would be valid in this context, wouldnt it? As mains water in a pressurised system would have better pressure than most vented systems...

The issue of unvented cylinders being incorrectly retrofitted is a by-the-way and doesn't negate the fact that I was stating.
Any incorrectly fitted device/system will cost money to fix, and will cause issues.

Thank you all the same for your attempt to try and get across what was in your mind

MOD NOTE: Cut out that attitude. You come on here looking for help and then berate the helper. This isn't a forum where you come to have your sensitivities messaged. You got an answer from someone that took time out to quickly answer question.

dathi

1.3 The cold water supply to the kitchen sink should
be taken directly from the service pipe supplying
water to the dwelling; the cold water supply to the
bath or shower and the washbasin and to other
appliances in the dwelling should be from a cold
water storage cistern. The bath, shower, washbasin,
and sink should also have a piped supply of hot
water, which may be from a central source or from a
unit water heater.

just for clarity the above is taken from the building regulations part G TGDs which states the cold water supply to bathroom should be from cistern but not necessarily the hot supply

Lenar3556

deravarra wrote: »

Rather than berate and belittle, I would have expected a little help.

For someone like myself who is not a professional to be asking advice to come across someone like yourself with the answers you give in the manner you give them is quite offputting.

Would you agree that an unvented system - which would be a replacement for a vented system - gives far more pressure than a vented system?

My information was gleaned from a few websites.

In one water cyclinder manufacturer's website, I saw the following:

A traditional vented cylinder requires connection to a water tank, usually in a loft or attic space, using gravity to deliver hot water to the home. ... An unvented cylinder uses a pressurised system, that has a direct feed from your cold water supply, so there is no need for a cold water storage tank in the loft or attic.

That itself would suggest that IT IS possible to connect the mains water. Perhaps you could take up the Irish water and building regs with them.

The "thats why we have unvented cylinders" comment would be valid in this context, wouldnt it? As mains water in a pressurised system would have better pressure than most vented systems...

The issue of unvented cylinders being incorrectly retrofitted is a by-the-way and doesn't negate the fact that I was stating.
Any incorrectly fitted device/system will cost money to fix, and will cause issues.

Thank you all the same for your attempt to try and get across what was in your mind

That attitude is very poor. He gave you good advice.

Unvented cylinders are more popular in the UK where there is a different standard of mains water supply and different building control regulations.

They are rarely used in domestic houses here as better results can usually be achieved with vented DHW systems at a lower cost.

Connecting directly to mains is likely to be a bad job, aside from compliance implications. Also you wouldn’t want hot and cold supplies to basins / showers etc. as different pressures. It would cause great difficulty.

Invest €500 or so in a quality twin impeller brass pump and pump the hot and cold post your existing cylinder.

Sleeper12

deravarra wrote:

A traditional vented cylinder requires connection to a water tank, usually in a loft or attic space, using gravity to deliver hot water to the home. ... An unvented cylinder uses a pressurised system, that has a direct feed from your cold water supply, so there is no need for a cold water storage tank in the loft or attic.

If you research combi boilers the website will say how wonderful it is to connect to the mains supply but they aren't talking about Ireland and its poor water network. In Ireland it is against the building regulations and local bylaws to connect these things to the mains supply. Apart from the regulations and bylaws it is bad practice & not the correct way to do it in Ireland

NewClareman

Sleeper12 wrote: »

If you research combi boilers the website will say how wonderful it is to connect to the mains supply but they aren't talking about Ireland and its poor water network. In Ireland it is against the building regulations and local bylaws to connect these things to the mains supply. Apart from the regulations and bylaws it is bad practice & not the correct way to do it in Ireland

You just educated me - I am considering a combi boiler and even Irish web sites are just copying the uk version. I am very surprised at sites such as Self Build and Grant Engineering which says "Mains pressure hot water on demand".

I understand (now) the requirement for a water tank. If I understand you correctly I can use a pump to create a pressurised system, that will then provide hot water on demand. Is that correct? (Ideally, I want to get rid of the hot water cylinder, altogether.)

Sleeper12

NewClareman wrote:

I understand (now) the requirement for a water tank. If I understand you correctly I can use a pump to create a pressurised system, that will then provide hot water on demand. Is that correct? (Ideally, I want to get rid of the hot water cylinder, altogether.)

That's correct. The pump will give you equal pressure on the hot & cold. You need to be careful getting quotes. Someone will give you a cheaper price and connect the boiler to the mains supply. Less work & no pump in the price.

deravarra

dathi wrote: »

1.3 The cold water supply to the kitchen sink should
be taken directly from the service pipe supplying
water to the dwelling; the cold water supply to the
bath or shower and the washbasin and to other
appliances in the dwelling should be from a cold
water storage cistern. The bath, shower, washbasin,
and sink should also have a piped supply of hot
water, which may be from a central source or from a
unit water heater.

just for clarity the above is taken from the building regulations part G TGDs which states the cold water supply to bathroom should be from cistern but not necessarily the hot supply

Thank you for clarity!

deravarra

Lenar3556 wrote: »

That attitude is very poor. He gave you good advice.

Unvented cylinders are more popular in the UK where there is a different standard of mains water supply and different building control regulations.

They are rarely used in domestic houses here as better results can usually be achieved with vented DHW systems at a lower cost.

Connecting directly to mains is likely to be a bad job, aside from compliance implications. Also you wouldn’t want hot and cold supplies to basins / showers etc. as different pressures. It would cause great difficulty.

Invest €500 or so in a quality twin impeller brass pump and pump the hot and cold post your existing cylinder.

Compare and contrast said response and that from Dathi.

Dathi provided the correct information in a friendly manner. And I appreciated that.

Sleeper12

deravarra wrote:

Compare and contrast said response and that from Dathi.

I think you read something that wasn't there with K.flyers post. He is extremely knowable on heating as this is what he specialises in. I have been told by other posters that he spent over an hour on the phone with them trying to resolve the issue over the phone. All professionals giving free advice here do not it because they want to help. He is definitely one of the good guys here.

I'm happy you got the information you needed

deravarra

Sleeper12 wrote: »

I think you read something that wasn't there with K.flyers post. He is extremely knowable on heating as this is what he specialises in. I have been told by other posters that he spent over an hour on the phone with them trying to resolve the issue over the phone. All professionals giving free advice here do not it because they want to help. He is definitely one of the good guys here.

I'm happy you got the information you needed

Since I am new to this particular part of boards, I will take what you say at face value.

I certainly wasn't looking for my sensitivities to be massaged as was suggested above. I would always be glad of advice from someone who is an expert - but took exception to what I thought was a little bit belittling of my lack of knowledge.

Dathi on the other hand shared the regs, and did so in a friendly manner.

Anyways, I think the issue has been resolved, and there's far more clarity here after all the posts.

Thank you