gravity vs mains hot water

[thedj]

Hi there,

I have looked around for a definitive answer to this question with no joy so here goes

I have a 1989 house with predominantly new heating. Ie new rads, new plastic pipe to them (they replaced the old micro boar with 15mm plastic). Also a brand new boiler. Echo tech from valient

The hot water though is old. There are two tanks feeding the hot water ( and a third for the heating before anyone asks) to a standard copper uninsulated hot water tank. About 1.5 m Max from top of copper to base of. Storage tank.

Obviously the hot water tank has to go.. it is pooring heat out like god knows what and the heat exchanger is so bad it takes 3hrs to get to temperature.

So do I replace almost like for like and bung in a new more efficient tank and a pump for the showers
Or
Go down the route of mains pressure hot water tank. ...loose the cold storage for hot water and not bother with pumps.

The copper pipes look good enough to hold the pressure. But I am trying to come up with pros and cons for both systems. .. one being cost... eg I can get a 110l stainless gravity fed tank for about 190 plus pumps from 100+.. so. Looking at around 350 for pump and tank (using better quality pump)
But for not much different I could do mains pressure.

Which is best... and in your opinions...why?


Cheers in advance

Ed

 

[Madrab]

Really all depends on your mains dynamic water pressure and flow. If this is all good to where the cylinder would be sited then an unvented hot water cylinder would be the best option IMO.
Good hot water pressure without pumping and the ability to feed multiple hot water outlets without a significant drop in performance.

 

[Agile]

An unvented cylinder needs to be fitted by a qualified person!

By 1989 the plain copper cylinder should have been foam covered to meet the building regs I would have expected!

I hope you realise you have to convert your gravity circulation to a fully pumped system.

Tony

 

[thedj]

Hi y'all, cheers for your replyes

Cylinder has about 1/4 inch of foam so is as good as nothing. (survey said needed replacing). And also, the coil is blocked/inefficient.

Mains preasure is fairly stable but id put a preasure valve on the supply to about 3bar.

Heating is pumped. Two valved system one for hot water tank one for heating.(New pump fitted)

Question....WHY does it need to be fitted by qualified person? What qualification is needed.
I ask as I am a qualified electrician, degree educated, can turn a hand to anything, so I aint stupid.I understand the need for preasure release valves and preasure limiting valves on supply. So is it a legal requirment (in which case it may be pumps and gravity) or what? (or just plummers protecting their livelihoods..no offense)

Cheers

Ed

 

[Terry lambert]

There is a you tube video of a cylinder blowing up, which goes someway to explaining why you need training to fit these.

Not all engineers and plumbers have this ticket either

 

[thedj]

Hi

I have looked on youtube and seen the mythbusters vid and one where it is on a crane rig.

the fact that it is staged implies that they are doing things that are not recommended.

any sealed cylinder will explode under the wrong pressure..
now most hot water cylinders are tested beyond 10bar. there is an expansion vessel to reduce internal pressures within the main tank, there is a pressure reduction valve on the mains cold water supply, there is a pressure release valve to the outside in the event of excessive pressure build up.... oh and a gauge to measure the pressures.

I can assume that incorrect installations would have one or more of these missing. and hence issues could be created. eg no release valve... could result in build up... no incomer reducer could allow fluctuations to be transferred into the tank...no expansion vessel would allow the heated water nowhere to expand to and increased internal pressures.

anything in the wrong hands can be a disaster waiting to happen. I know how to wire a house.. but a (part P) kitchen fitter could do the same thing and wire a house in nothing but bell wire... it would work for a bit. but IS a disaster waiting to happen. turn on the oven or a few bulbs and fire time is inevitable

never underestimate the idiocy of human kind....

I do appreciate the warnings but trust me I do know the practicals of the installations (maybe due to some training that allows me to work on fairly complex gas systems in very tightly controlled circumstances giving me an incite to pressurized pipe networks)

what i dont get is the pros and cons of each system... If is just a question of price and ability to install then i guess pressured is best... but if anyone can come up with the pros on gravity systems i am all ears

cheers

ed

 

[Agile]

I ask as I am a qualified electrician, degree educated, can turn a hand to anything, so I aint stupid.I understand the need for preasure release valves and preasure limiting valves on supply. So is it a legal requirment (in which case it may be pumps and gravity) or what? (or just plummers protecting their livelihoods..no offense)

Cheers

Ed

If a qualified electrician then you should be aware of Part P ?

Similarly under the Building Regulations there is a section ( used to be G3 ) which covers unvented cylinders!

There you will find the requirement for anyone installing these to be appropriately qualified. 1-2 two days course costs about £300.

I am surprised as an electrician that you are not aware of the Building Regulations!

Tony

 

[Agile]

Heating is pumped. Two valved system one for hot water tank one for heating.(New pump fitted)

Cheers

Ed

If the cyl heating coil is pumped then you don't have gravity hot water.

BUT in that case the HW should reheat in 30-40 minutes and not three hours!

Tony

 

[Galoka]

Heating is pumped. Two valved system one for hot water tank one for heating.(New pump fitted)

Cheers

Ed

If the cyl heating coil is pumped then you don't have gravity hot water.

BUT in that case the HW should reheat in 30-40 minutes and not three hours!

I think the OP mean the HW cylinder is gravity fed by the CWSC in the loft, rather than a gravity HW heating system.

(I fell foul of this confusion in another thread recently)



Ah, I fell foul of this confusion in another thread.

 

[Madrab]

Basically it is written into legislation that unvented installations must be conducted and signed off by a suitably qualified person, by the HSE, in line with the building regulations. Just as a Gas engineer must be gas safe registered to install and sign off a gas installation, or an electrician must have his 17th Edition etc to sign off their work.
We all know that anyone with enough savvy can do the work or the installations but when it comes to future issues or the law, then each must hold the relevant qualification to prove they are competent.

 

[Galoka]

AIUI though, you do have to be suitably registered to install an unvented cylinder, not just to self certify the installation.

Elec is a bit different, I can DIY notifiable work, I just need to notifiy building control.

 

[Galoka]

AIUI though, you do have to be suitably registered to install an unvented cylinder, not just to self certify the installation.

Elec is a bit different, I can DIY notifiable work, I just need to notifiy building control.

I didn't think there was provision for this sort of thing with unvented cylinders

 

[thedj]

Heating is pumped. Two valved system one for hot water tank one for heating.(New pump fitted)

Cheers

Ed

If the cyl heating coil is pumped then you don't have gravity hot water.

BUT in that case the HW should reheat in 30-40 minutes and not three hours!

Tony

Gravity fed... hot water
Ie tanks in loft to supply cold water to the heating tank or cylinder.... pump moves the water from boiler through the rads and through the heating coil in the heating tank or cylinder.

 

[thedj]

I ask as I am a qualified electrician, degree educated, can turn a hand to anything, so I aint stupid.I understand the need for preasure release valves and preasure limiting valves on supply. So is it a legal requirment (in which case it may be pumps and gravity) or what? (or just plummers protecting their livelihoods..no offense)

Cheers

Ed

If a qualified electrician then you should be aware of Part P ?

Similarly under the Building Regulations there is a section ( used to be G3 ) which covers unvented cylinders!

There you will find the requirement for anyone installing these to be appropriately qualified. 1-2 two days course costs about £300.

I am surprised as an electrician that you are not aware of the Building Regulations!

Tony

I am aware of part p... it is a money making govenment scam and a pain in the ass.
It is the main reason I gave up doing jobs on the side for extra cash / mates etc. As to self cert requires a course that costs 800 plus. Per year. So ain't worth it.
However as pointed before, a kitchen fitter could rewire a house under part p and be covered and self cert. Where I who have 2391 , 17th, many years on the trade. Can now no longer do bits and bobs as and when without the outlay of load of money.
Which I why I know I shouldnt have put a new consumer unit in my own house without loads of paperwork and lining the pocket of someone else.....but it is tested correctly, installed correctly.. and yes I would trust my work over others any day and put my kids life on it