Accumulator or Break Tank

[ln1234]

Hi,

I am looking to boost the water flow rate from mains into an unvented cylinder, and wanted some advice on whether to go for an accumulator or a break tank/pump set in a new installation. I have been reading some old threads about this, but they have confused me even more.

My water flow rate is around 10-12 litres per minute, at around 2 bar. The tanks & boiler will be housed in a small shed on the side of the house, and noise shouldn't really be an issue.

I like the idea of a tank and a pump set, but not sure what the are like to live with in terms of running costs and maintenance. What would you recommend?

Thanks

 

[bengasman]

You don't need a break tank, you need to check your incoming mains for restrictions; 2 bar is fine. You probably have either a dodgy stopcock, or a buckled/corroded pipe somewhere.

 

[ln1234]

You don't need a break tank, you need to check your incoming mains for restrictions; 2 bar is fine. You probably have either a dodgy stopcock, or a buckled/corroded pipe somewhere.

If it is a pipe restriction and it is fixed, what kind of flow rate can I expect through a standard lead pipe at 2 bar?

 

[bengasman]

Depends on the size and type of lead pipe.

 

[ln1234]

Depends on the size and type of lead pipe.

You know a lot more than I do (and I appreciate the responses) but i'm confused at your responses. How could it be suggested that my 2 bar pressure is sufficient, if we don't know the pipe sizes, and hence can't calculate the flowrate I should be getting if there were no pipework restrictions?

My problem at the moment is that i'm getting around 10-12 litres per minute and i'd like to run a system boiler and unvented cylinder. I think our requirement will be a max load of around 25litres a minute so would need a solution that could cope with this as well as be low(ish) maintenance. I know my incoming pipe from the street could be changed, but I think the cost of that would be around £3k and there is no guarantee of the flowrates i'd get through this.

There have been posts by members of this site of break tanks/accumulators being installed and I wanted to get opinions of each, with possible recommendations of which route we could go down.

Thanks

 

[bengasman]

How could it be suggested that my 2 bar pressure is sufficient, if we don't know the pipe sizes, and hence can't calculate the flowrate I should be getting if there were no pipework restrictions?

Common misunderstanding.
A distinct lack of pressure (below 0.5 bar) will give a poor flow, but apart from that, it is mainly the pipesize that determines the flow. The pipesize has nothing to do with static pressure; you can get 10 bar through a 6mm pipe

A break tank plus pump are used to solve extremely low pressures. To get a performance to justify an unvented cylinder( 25+ litres a minute at 2 - 3 bar), you would be talking about thousands of pounds worth of kit.

I know my incoming pipe from the street could be changed, but I think the cost of that would be around £3k and there is no guarantee of the flowrates i'd get through this.

At 2 bar, increasing from a lead pipe to 32mm blue is guaranteed to have results. How far is your internal stopcock from the streetvalve? I find it hard to believe in London it would be so far 3000 squid would not give you enough flow to fill a pool in a couple of minutes. Maybe a bit exaggerated, but you get my drift.
Half a mile through 5 feet of concrete drive?

The question is: do you need all this? Upgrading your mains may not cost £3000, it will still be a fair bit. A decent unvented cylinder, properly installed will set you back about £1500, and is unknown if your boiler will pull it, and how much longer that will live.
What are you trying to achieve with your higher flow?

 

[ln1234]

Looks like I have oversimplified and misunderstood pressure and water flow!

We have 2 bathrooms and I wanted to have a system that would give great shower pressure, as well as being able to cope with a busy kitchen. It's doubtful that both showers would be on at the same time, but I would like the system to be able to cope with a decent amount of flow - especially since we're refurbishing the whole house and can manage with the disruption.

i've just been reading a bit about the area and it's quite notorious for bad water pressures. This is partly due to being on a hill, and thames water's issues with pumping water up to this level.

Do you think I should explore changing the pipe to 32mm or are there alternatives I could consider?

Appreciate you helping me out!

 

[bengasman]

2 bar is fine, no need for more
Depends what you mean by great shower pressure. Do you want loads of water coming out the shower head? Do you want the water to hit your body like a massage system? Both?
What boiler do you have currently?
Remember that water flow is as good as the narrowest passage. To get what I would classify as a greatshower, you would need at least 32 mm plastic from the street valve, and 28 mm internal splitting off in 22 to cylinder and bathroom to guarantee great flow without interruption. That means effectively replumbing most of the house
Cylinder upwards of 400 litres, which will need floor support before installation. I have one client who has this, and it is a great shower, but cost stupefying amounts of money.

 

[GeorgeBramwell]

I have just read this thread. In your situation I would fit a quality high flow combi that can cope with two showers simultaneously and fit an accumulator. This is by far the most cost effective route. Look at the ATAG 51kW, W-Bosch 550 Highflow floor mounted or Ethos 54kW. I have had great success with the ATAG and an accumulator, and fit the external temperature sensor to set up the weather compensation. The W-Bosch does not come with weather compensation. At a push a W-Bosch 42kW would do, as it will do two showers at a slightly reduced flow rate.

Connect the kitchen tap before the accumulator and maybe the washing machine and dishwasher too. Then these taps do not rob the outlets off the accumulator.

The secret with mains pressure systems is to balance the water system. Taking the kitchen off the accumulator helps and installing flow regulators on toilets and other taps. They do not need 10 litre/min running them. Have a 22mm pipe to the combi from the accumulator. At the accumulator tee off for the cold supplies, so all these are on one line. Replace the stop tap with a full bore 1/4 turn tap and turn it every 6 months to ensure it does not seize up.

Accumulators are easy to fit.

With an accumulator, if there is a water cut your water keeps running, well the taps off the accumulator do.

 

[Biggles..]

if your looking to boost look into Grundfos home booster.

 

[ln1234]

I have just read this thread. In your situation I would fit a quality high flow combi that can cope with two showers simultaneously and fit an accumulator. This is by far the most cost effective route. Look at the ATAG 51kW, W-Bosch 550 Highflow floor mounted or Ethos 54kW. I have had great success with the ATAG and an accumulator, and fit the external temperature sensor to set up the weather compensation. The W-Bosch does not come with weather compensation. At a push a W-Bosch 42kW would do, as it will do two showers at a slightly reduced flow rate.

Connect the kitchen tap before the accumulator and maybe the washing machine and dishwasher too. Then these taps do not rob the outlets off the accumulator.

The secret with mains pressure systems is to balance the water system. Taking the kitchen off the accumulator helps and installing flow regulators on toilets and other taps. They do not need 10 litre/min running them. Have a 22mm pipe to the combi from the accumulator. At the accumulator tee off for the cold supplies, so all these are on one line. Replace the stop tap with a full bore 1/4 turn tap and turn it every 6 months to ensure it does not seize up.

Accumulators are easy to fit.

With an accumulator, if there is a water cut your water keeps running, well the taps off the accumulator do.

Thanks for this - are there any accumulators you could recommend?

 

[ln1234]

if your looking to boost look into Grundfos home booster.

I looked at that but it states you can't put it outside - i'm thinking of installing in wooden shed on the side of the house (it will be insulated as best I can)

 

[Biggles..]

sheds/outbuilding are somewhat differnt to being put outside.You wouldnt get manufacturers recommending accumulators directly situated outside.

 

[GeorgeBramwell]

sheds/outbuilding are somewhat differnt to being put outside.You wouldnt get manufacturers recommending accumulators directly situated outside.

In an insulated shed with no large holes using T&G shiplap, with a proper sealed door (not the shed type rickety doors) they would approve. With an accumulator you can put a cylinder Jacket over it to add more insulation. It takes a lot of cold sustained weather to freeze a large body of water as in an accumulator. Pipes freeze easily as there is only a small body of water inside. Freezing water only starts at 0C. Bear in mind, moving water resists freezing.

Many boiler manufacturers have no problem with boilers being in insulated sheds, as many have auto frost protection and if not insist on frost protection being external to the boiler. I have fitted many boilers in wooden lean-to's. In jobs where space is a problem I always suggest this option. For £500-600 a suitable lean-to can be built behind the house by a local shed company. £500 is a small amount to save a lot of space that maybe an en-suite shower room. They are ideal as all the servicing (and any leaks) and noise is outside the house. Usually the customer is delighted at not having boiler on the kitchen wall. I try and use plastic pipes through the walls into the house to reduce pump noises and add value against frost as plastic resists frost far better than copper. Many boilers can have plastic run right up to the boiler. Any pipes have 25mm pipe insulation and no gaps.

Reliance make a decent accumulator with a replaceable membrane. Many companies make them. Whatever the stated volume of the accumulator half it for the stored water volume.

You may only need it for DHW. That is all the cold only taps (without mixers) not taken off the accumulator, take off the mains pipe before the accumulators non-return valve. The cold for w/machine, d/washer and toilets need not be off the accumulator. Then the size may be smaller. The accumulator acts as a storage vessel in case of water outages. You have to consider if you need 100% water storage. If you do as water outages are common, it may be worth it to buy a large accumulator as space may not be a problem in the shed. The larger the more water storage.

Accumulators are easy and simple and no noise. If the charge drops it is pumped up with car pump, one off the battery is easier. Even replacing the membranes is easy and a DIY task. They make high flow combis really sing, as other outlets do not affect the water pressure or flow when piped up right.

 

[simond]

Certain makes of accumulator are available with a insulating jacket. They can be sited outside, they will need a shed or similar.

We succesfully buried one last year.

You can also boost them with a charger pumpset, to lift the pressure to 3 or 4 bar. I have photos of such installations if you email me.

Break tanks are old hat and best avoided. There is very little justification for fitting such things in domestic environments where periodic bacterial protection is unlikely to be considered. Especially in this hot weather. Not to mention the noise.