Gravity hot water system - replace or improvement ideas please advise

[Sup9]

Hello all,

I currently have a gravity hot water system - with a 110x60x60cm water tank and a small one (expansion vessel?) in the loft, the water pressure in the bathrooms (3 on first floor) are very poor, especially the master bedroom en-suite (the furthest way from the cold water tank) which is unusable for shower. My understanding is that the cold water tank is feeding both the hot water cylinder and the cold water taps in all bathrooms. And I have tested at the ground floor tap, the mains water is 22L/mins so not so bad at all.

I also had a look in the loft and find out the cold water tank is the old style open tank with plastic sheet covers on top, which already fall off into the tank so the tank is quite dirty and I can see the built up limescale at the bottom.

So apart from the shower pressure I have the concerns about the water quality.

My understanding is that I have two options:

1. Keep the existing system with the loft cold water tank. Add multiple small pumps for each bathroom, and change the cold water tank to poly water tank with lid. This system is the safest system as the tank and cylinder is not pressurized, but the water quality could be getting worse along the time when the limescale built up and dust etc get into the tank.

For this setup my main concerns are Water quality over time and pump noise. Do people just get the tank professionally cleaned regularly? Or can I by pass the cold water tank and split the mains water (currently feeding the cold water tank) then connect all bathroom cold water pipes to it, so my bathroom cold water taps are feed directly by mains water - fresh and at the mains pressure. Then adding pumps for each bathrooms' hot water to balance off the pressure.

2. Convert to unvented cylinder, so the cold water will be at mains supply pressure. With 22L/min flow rate tested at ground level tap, am I guaranteed to have good shower performance in all bathrooms ( assuming only one in use or 2 showers simultaneously). And we are also slightly worried about the safety of the cylinder as it may blow up if not fitted right - I was not aware it could explode and cause serious damage, the cylinder fitting guy came for a quote and asked me to check out the explosion video - he was trying to make a selling point as he's manufacture approved installer and I am seriously put off by the possibility of it exploding.

The current cylinder is in the cupboard next to my daughter's room so my wife asked me to move the unvented cylinder to the garage if we went with the unvented, but then my double garage would become single as I cant park two cars anymore with the cylinder installed there...

Considering I will be living in this house for a long time so the cost does not play much here, only looking to the best option for the long run.

Thanks a lot for any advice in advance.

 

[Last Plumber]

If I were you I think I would go for the unvented option.
You need a good, G3 compliant Heating Engineer to come and advise you first, without filling you with fear.
These systems have been around for many many years and are used in a variety of situations.
If installed and maintained correctly, they are just as safe as anything else.

If you have gravity hot water ( presuming you mean what I think you mean ) you will need advice on the boiler/system side too, as it will need to be upgraded.

I hope this helps.

 

[Harvest Fields]

I would go for an unvented system also. That is the only way to get anywhere near the flow rate you have at the minute. It would also mean you could run more than 1 bath/shower at a time with no hassle of losing pressure. The initial cost of the install/setup of the system may put some people off, but in my opinion the long term benefits out weigh this cost.

 

[Sup9]

If I were you I think I would go for the unvented option.
You need a good, G3 compliant Heating Engineer to come and advise you first, without filling you with fear.
These systems have been around for many many years and are used in a variety of situations.
If installed and maintained correctly, they are just as safe as anything else.

If you have gravity hot water ( presuming you mean what I think you mean ) you will need advice on the boiler/system side too, as it will need to be upgraded.

I hope this helps.

Thank you. I had a manufacture approved installer came for a quote and he said I can replace the cylinder for now and boiler at later time if I wanted, should I have someone else come for a second opinion on whether my boiler would cope with the new cylinder?

So if all things done right (good quality cylinder, manufacture approved installer etc), I should not worry install the unvented cylinder between the bedrooms on first floor? or would it worth the hassle to move it to the loft or garage just for the extra peace of mind...

 

[Jay The Plumber]

you can locate the unvented cylinder in the loft or garage yes, you can even get horizontal cylinders designed for lofts.. your installer will be able to advise you on this regarding the cold feed and the cylinder location.

 

[Last Plumber]

Thank you. I had a manufacture approved installer came for a quote and he said I can replace the cylinder for now and boiler at later time if I wanted, should I have someone else come for a second opinion on whether my boiler would cope with the new cylinder?

So if all things done right (good quality cylinder, manufacture approved installer etc), I should not worry install the unvented cylinder between the bedrooms on first floor? or would it worth the hassle to move it to the loft or garage just for the extra peace of mind...

As above.
Have no fear form the unvented Cylinder !
Trust me, I'm a Plumber.

 

[Sup9]

Thanks all, I've done some more research and with the feedback here I think I'll go with unvented cylinders. now will look into costs and installers etc.

 

[Last Plumber]

Have a look at the dual coil type. They're not that much more expensive and it would give you options for a later date, such as adding solar.

 

[Sparkgap]

There's a lot of scaremongering about risks with unvented systems but the reality is there isn't a problem if things are done right. Taking an example, if you're running the unvented cylinder off your heating boiler the only way you could have an explosion would be for all the fail-safe devices on the boiler to fail, the heating system somehow to get the cylinder above 100C, all the safety devices on the cylinder to fail as well as the pressure exceeding the rating for the cylinder etc. etc. You see what I mean! Can't say it MIGHT NOT happen, but the chances are 1 in 10-to-the-power-of-my-overdraft!
And for those who say a vented cylinder is safer, the only cylinder I've seen explode was a 600 gallon vented one: some yobs torched the chemistry lab in a local secondary school where the hot water pipes ran through the ceiling. Water flashed to steam, blew back to the boiler room next door, blew the bottom out of the cylinder which leapt 3ft into the air hitting a 5" gas main. Fire brigade turned up to find a fire, chemicals, flooding and a gas leak! Fun for everybody

 

[brum]

Unvented all the way...brum

 

[Pro heat]

I agree with all, go for unvented system But can be dangerous if installed by unprofessional person,

 

[Chuck]

I've just had a gravity circulation HW system replaced with an unvented indirect cylinder (Megaflo) getting rid of both CW store and CH header tank in the roof in the process. It was not cheap but I am really pleased with the new system. (I don't have a shower in the bathroom at the moment but it would make installing one very easy.).

The only 'gotcha' was the airing cupboard went from toasty with the old cylinder to barely warm with the Megaflo. Fortunately, space and wiring made installing a couple of low surface temp heaters and a 1-4 hour timer easy, but you may want to plan for this as part of the installation.

Make sure you use an installer with a G3 ticket (you can check them on the gassafe website) and make sure they issue a building regs compliance certificate.

C.

 

[doitmyself]

I currently have a gravity hot water system

Does the timer allow you to have central heating on by itself, or do you have to have the hot water on at the same time?

 

[Last Plumber]

Does the timer allow you to have central heating on by itself, or do you have to have the hot water on at the same time?

Hello doitmyself,
You shouldn't be able to put Heating only on with gravity hot water !

 

[Welder]

Couple of additional points.
1 - G3 compliance is NOT listed on Gas Safe site. Each installer carries a card with their details - check it.
2 - Water flow rate is VITAL for an effective UV system. You must make sure the installer knows exactly what you expect from the system into the future.
3 - Make sure it is serviced EVERY year

 

[ShaunCorbs]

Couple of additional points.
1 - G3 compliance is NOT listed on Gas Safe site. Each installer carries a card with their details - check it.
2 - Water flow rate is VITAL for an effective UV system. You must make sure the installer knows exactly what you expect from the system into the future.
3 - Make sure it is serviced EVERY year

1 it is under unvented cylinders

2 agree 100% (min I would do is 2.0 bar and 25lpm)

3 agree, if it fails and you haven't had it serviced your house insurance could be invalidated

 

[Welder]

Shaun thanks
What I really meant was that the GS site is NOT the only where G3 registration is listed. For example I'm not GS but am G3. Now I look at it, I can't find a website for mine!!

 

[ShaunCorbs]

Shaun thanks
What I really meant was that the GS site is NOT the only where G3 registration is listed. For example I'm not GS but am G3. Now I look at it, I can't find a website for mine!!

Thing where gs scores is we only have to pay 2.50 to register an unvented cylinder building control want a lot more

And there isn't one for people to check, just have to show your card and advertise your G3

Also welcome to the forum

 

[cr0ft]

To allay your fears about unvented cylinders OP, I had to cut one out that was leaking and corroding badly (10 years old, never been serviced) and replace it. The drain valve had failed and I wasn't able to syphon all the water out so had to cut a hole in the top to wet vacuum the rest of the water out so I could get it downstairs on my own.

The inner skin of the cylinder is about 5mm thick stainless steel. Strong as anything and took me an age with an angle grinder to break through!

 

[doitmyself]

Hello doitmyself,
You shouldn't be able to put Heating only on with gravity hot water !

I know that! However you are assuming that the OP is talking about a pumped heating/"gravity" hot water system. We don't know that. Some people refer to a fully pumped with cold water, from a tank in the loft, feeding the HW cylinder and hence the hot taps as having a gravity HW system, presumably as compared to a direct feed from the mains, i.e unvented cylinder.

I was trying to find out what the OP meant by "gravity HW system".

 

[Last Plumber]

I know that! However you are assuming that the OP is talking about a pumped heating/"gravity" hot water system. We don't know that. Some people refer to a fully pumped with cold water, from a tank in the loft, feeding the HW cylinder and hence the hot taps as having a gravity HW system, presumably as compared to a direct feed from the mains, i.e unvented cylinder.

I was trying to find out what the OP meant by "gravity HW system".

You are right, I am thinking the OP is talking of a gravity Hot water system.

I answered your post because I thought you were confused about something on your own system and I was trying to help you,

Going of the description and other replies I do think he/she is talking about a gravity hot water system but If i'm wrong fair enough, it is just how it reads to me.

To the OP:-
When you say you have a gravity hot water system what do you mean?
Do you mean that you have pumped central Heating and gravity hot water or is it fully pumped, just so we can all be on the same page?

Not that it's relevant if you're asking about a new system anyway but just so we know what your current system is.

 

[doitmyself]

You are right, I am thinking the OP is talking of a gravity Hot water system.

Unfortunately you have fallen into the same trap as the OP - it's so easy!! Do you mean a pumped heating/gravity HW system, or a fully pumped system with a cold tank in the loft feeding an unvented HW cylinder?

Fortunately your question to the OP is clear.

 

[Last Plumber]

Unfortunately you have fallen into the same trap as the OP - it's so easy!! Do you mean a pumped heating/gravity HW system, or a fully pumped system with a cold tank in the loft feeding an unvented HW cylinder?

Fortunately your question to the OP is clear.

I haven't fallen into a trap at all.
I know what I am talking about.

If the OP is describing something in a misleading way or if he / she is using incorrect terminology that is not a fault of mine.

It is understandable of course as there are a lot of do it yourself people and laypersons, who use this forum for information.

Just to be crystal clear with you.
I am thinking that the OP has an open vented, tank fed domestic hot water cylinder, made from copper, which is heated using gravity circulation from a boiler.

Is that what you think ?


Most heating engineers or plumbers discussing gravity hot water would be thinking of how the water is heated as opposed to it being mains or tank fed !

 

[ShaunCorbs]

Unfortunately you have fallen into the same trap as the OP - it's so easy!! Do you mean a pumped heating/gravity HW system, or a fully pumped system with a cold tank in the loft feeding an unvented HW cylinder?

Fortunately your question to the OP is clear.

I maybe thinking of someone else but wernt you banned last year ?

 

[rpm]

I maybe thinking of someone else but wernt you banned last year ?

Yes he was, think it was for arguing about signing off boiler installs done by somebody else or something along those lines concerning gas works.
Shaun, everyone was unbanned as part of the recent restructure.