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We have a traditional Vented system with a feed from our gas boiler for hot water as well as an immersion heater to which we added an iBoost Solar diverter recently. This provides us with hot water when we have excess solar from the PV array. We only added this in November and I am impressed how much it has delivered over the last couple of winter months and I hope it will be even more effective as the days lengthen.
Our current tank is a bit small as well as old with a couple of leaky connections. My future SIL is a plumber so with me providing labour I would like to replace it with a similar but much better and bigger tank. Would like to keep same immersion and gas solution for hot water and the current vented design.
What are my options and what would STW do? I have quite a lot of space so a much bigger tank is not a problem.
What are my options and what would STW do?
I'd talk to your SIL!
HTH 🙂
Is she able to fit an unvented system? - because that's undoubtedly what you should fit.
With regards to size I'd possibly go as big as you can fit - 250L is probably the smallest I'd go now but the bigger it is the more it will cost to heat in the winter (the PV won't completely heat it unlike the 6 'summer' months.
I'd also consider used tanks off eBay. I paid £120 for a used 225L Megaflo that's in our other place that and it's been perfect. That was about 8 years ago though and prices have definitely gone up!
Edit: Just seen that you want to keep a vented system...... why would you/anyone want to do that? Do you have poor water pressure/flow?
I’d talk to your SIL!
Of course I have and although he is very young his experience is quite traditional and his solution is to simply replace like for like (but larger) and that may be exactly what we do but I was interested in a solution which is possibly more future proof and maybe uses newer technologies.
In that situation I'd go as big as I could physically/structurally fit (water is heavy) with as many inputs as you can (PV diverter, solar thermal if you can, immersions at base and halfway up the side, wood burner if you have/use one, main feed from boiler) You don't have to heat the whole tank all the time, as it'll draw from the top remember. But a typical bath takes c180 litres of water, so I'd want a tank with the capacity to fill that with hot, with some over for other uses, particularly as tanks get cooler the further down you get.
Edit: Just seen that you want to keep a vented system…… why would you/anyone want to do that? Do you have poor water pressure/flow?
Our house was built using 10mm piping and we have "medium pressure". Speaking to a couple of plumbers installing an unvented system would increase the pressure and increase likelihood of leaks. I would like to replace all of the piping and will each time I have the opportunity but its likely to be quite some time until it is done, any sooner would likely mean an expensive divorce. Interested in your Megaflo solution. What does that offer in addition???
with as many inputs as you can (PV diverter, solar thermal if you can, immersions at base and halfway up the side
Thanks. Do all larger tanks offer multiple feeds like this? Wonder how or if I could alter my iBoost (which feeds a single top immersion coil) to fit....
Edit: iBoost feeds up to 2...
Speaking to a couple of plumbers installing an unvented system would increase the pressure and increase likelihood of leaks.
Well..... possibly, but that's rediculous!!
Fitting an unvented system means that your hot water pipes will be under exactly the same pressure as your cold water pipes (because the hot water is pushed out of the tank by the incoming mains pressure).
Unless your hot water pipes been fitted worse than the cold water pipes then there's no difference!
A Megaflo is simply an unvented tank - other makes are available!
An unvented system will remove the requirement of a tank in the loft thus reducing the chances of a burst pipe as well as supplying balanced hot and cold water at the same pressure throughout the house.
Thanks for that. No reason to believe hot piping more shoddy than cold. TBF the plumbers didnt say dont do it they just highlighted it as a slightly increased risk when we were discussing replacing the heating boiler as the hot tank is pressurised I understand. I assume Megaflo do vented as well? Removing the tank is only a small benefit but slightly increased hot water pressure (which I understand is a benefit of an unvented tank) would be helpful.
Drain and seal off the hot water side temporarily and pressurise it to 3 bar with a track pump. If it doesn’t leak or explode, it’ll probably be fine.
I am not a plumber.
Removing the tank is only a small benefit
Until it leaks 😉
Less pressure, as you use a prv to lower the incoming pressure to the rated cylinders pressure, which is a maximum of 3bar, so if your direct tp mains you might have 3.5bar on the cold, or more.
10mm pipes should be no more leaky than 15mm.
Good point but it seems that 3.5 bar is on the high side for average water pressure so the chances are the pressure's are pretty similar.
I have the same set up.
Recently got a new boiler but kept the hot water tank and solar I boost.
Then the tank developed a leak that couldn't be fixed so I replaced it with a bigger tank and a titanium immersion as they last longer.
I was hoping to get more free hot water but I ended up with less. Turns out the new immersion heater was shorter so didn't go down into the water as far so heated less water even though the tank was bigger.
With hindsight I should have considered a tank two immersion, one at the bottom and top.
At some point I need to replace my immersion with a longer version and hope that heats more water.
Definitely worth looking at where the immersions are located then!
Megaflo's have the immersions inserted horizontally from the side with larger tanks having a lower and upper (I think only one is fitted initially but it depends if it's a direct or indirect tank)
Due to upcoming retirement I was idly looking at indirect unvented tanks for hot water as part of a serious re-model of the hot water supply and our third bedroom. I stumbled upon OSO tanks from Norway that (using a Delta tank) are A rated. A little more expensive (£5 for my size compared to a similar sized Mega-flo) but given fuel costs that may well be a payback in a couple of years.
Now to find out if my plumber has any experience of them.
Now to find out if my plumber has any experience of them.
The aprtment my daughter is living in this year has an OSO cylinder - looks neat.
Their data shows 1.13kW heat loss per day which equates about 4c drop/day on a 250L tank. The real life [3 day old, in
a house that is currently unheated] data from one of my tanks shows a loss of 4c/12 hours - so it compares favourably depending upon the price difference.
I'm not sure how that is tested but I've found that there's a fair amount of heat lost from the pipework leaving the tank.
Speaking to a couple of plumbers installing an unvented system would increase the pressure and increase likelihood of leaks.
Sounds lots like the plumbers you have spoken to have not been qualified to install unvented tanks.
The answer to this is yes , and no .
If its gonna leak , its gonna leak whatever the psi . Vented with a reasonble head say 5psi , or unvented at 42psi . If there's a hole or weak joint 5psi will leak , it would just leak more at 40psi.
Fit a high gain unvented cylinder then it will be ready for a heat pump in the future.
You could even install as vented at the moment if you wanted and convert to unvented later if you want.
As others have said jointing of pipes doesn’t differ so higher pressure should be irrelevant.
If you have 3 bar going into the cylinder then you will have more coming out because you have heated it, typically around 4.5 I think.
With unvented it is crucial you do a pressure and flow test to check how it will perform, also crucial to consider is discharge pipework route.
Sounds lots like the plumbers you have spoken to have not been qualified to install unvented tanks.
How do you know?
If its gonna leak , its gonna leak whatever the psi . Vented with a reasonble head say 5psi , or unvented at 42psi . If there’s a hole or weak joint 5psi will leak , it would just leak more at 40psi.
There are no holes and it doesnt leak now. My concern is that the additional pressure may create leaks in the rubbish piping in the floors etc. I think its true that greater pressure can create leaks, do you agree? although I didnt think they ran at 42psi.
Fit a high gain unvented cylinder then it will be ready for a heat pump in the future.
You could even install as vented at the moment if you wanted and convert to unvented later if you want.
Thats interesting. Being ASHP ready would be useful.
How do you know?
Because nonsense reasons not to fit an unvented tank.
Had they said "insufficient water pressure for unvented" it would have been more credible
Had they said “insufficient water pressure for unvented” it would have been more credible
They both wanted to fit it and proposed it as the best solution. They also both highlighted a small risk that due to the (?psi) increase in pressure it may increase the likelihood of a leak in some of the older house piping.
I’m not sure how that is tested but I’ve found that there’s a fair amount of heat lost from the pipework leaving the tank.
That's part of my remit too, with pipework insulation being considered for reducing summer fuel usage and also cutting the temperature in the bedroom as guests complain of sleeping in a sauna. Winter losses just help to reduce the gas burn for the radiators upstairs.
(Some of the losses are attributed to the poorly fitting jacket in the past and also undersized pipework feeding the coil).
You could say we bought the heating equivalent of an @molgrips car 🙂