Accumulator or Pump to boost water supply?

[Ferdinand]

Elsewhere I have talked about my project this year to upgrade my two bathrooms.

 

One aim is to have 2 showers that can be run simultaneously. I have a big Combi that is well able to do it heat wise. 

 

My current flow measurement at the cold kitchen tap on full is about 9-10l per minute. I may have scope to up the pressure slightly.

 

I am happy to embrace eg shower heads which use less water.

 

There will be one electric and one mixer showers.

 

The plumber has initially recommended a boost pump, rather than the accumulator I was think about.

 

Can anyone comment on pros and cons, and any measurements I need to make to help making the best decision.

 

Thanks

 

Ferdinand

[Cpd]

In the cabin I have an electric shower and the low water pressure light would come on and you had all the usual hot / cold that happens when things are just not working well ! I fitted a grunfos water pump that comes on to bring the pressure up to 2 bar it works seamlessly and you can have a shower as hot as you want with consistent pressure. It transformed the shower experience and our guests love the shower experience! It only comes on automatically when the shower is running and therefore you don’t notice the noise, it switches off as soon as you turn the shower off.  Not sure if this is what your looking for or are you going for a full house pressure system.

 

i am NOT on mains water but a private spring so I can do as I please ! 

Edited April 14, 2019 by Cpd

[Big Jimbo]

I used a pump on my daughters incoming mains to boost it to 1.5 bar. Works well. I think you can get more powerful one's but i think you might need the water boards permission to fit on bigger than 1.5 bar.

 

[ProDave]

I thought you were not allowed to use a pump to suck water out of the water main?

[Jeremy Harris]

25 minutes ago, ProDave said:

I thought you were not allowed to use a pump to suck water out of the water main?

 

You're aren't, it's a breach of the water regs if you create suction at the main, a big no-no, as it risks contamination being sucked into the mains water supply through any leaks (and all water mains have leaks).

 

If you need to add a pump set, then it needs a break tank, to remove all possibility of creating suction on the main.  The alternative is to fit an accumulator, fed from the main via a NRV, which will store water at the peak pressure from the main under low demand conditions, so allowing water to be drawn off later at high pressure and flow.

[Big Jimbo]

20 minutes ago, JSHarris said:

 

You're aren't, it's a breach of the water regs if you create suction at the main, a big no-no, as it risks contamination being sucked into the mains water supply through any leaks (and all water mains have leaks).

 

If you need to add a pump set, then it needs a break tank, to remove all possibility of creating suction on the main.  The alternative is to fit an accumulator, fed from the main via a NRV, which will store water at the peak pressure from the main under low demand conditions, so allowing water to be drawn off later at high pressure and flow.

I think you are wrong. A 1.5 bar pump on the mains will not draw in more than 12Lts of water a min, and are  therefore not a problem. You only need to go all high tech, and expensive if you want to pull in more than 12lt. This was confirmed for me by the water company.

[Jeremy Harris]

15 minutes ago, Big Jimbo said:

I think you are wrong. A 1.5 bar pump on the mains will not draw in more than 12Lts of water a min, and are  therefore not a problem. You only need to go all high tech, and expensive if you want to pull in more than 12lt. This was confirmed for me by the water company.

 

I'm not at all wrong, check the regs.  You must not allow suction to occur on the main at any time, and you have no way of knowing, with a directly connected pump set, what the mains pressure is when the pump is running.  The flow rate is neither here nor there; it's the dynamic pressure in the main that's critical.  If the water company have advised you that direct connection of a pump set to their main is legal, without some form of positive control measure to guarantee that the pressure at the main connection cannot drop below the minimum positive pressure required to ensure that contamination is never drawn into the main, then they are wrong.

[Big Jimbo]

I'm sure you are right John, just saying what the Water company told me when i wrote to them. I believe that the smaller intelligent pumps will regulate to ensure that a max of 12lt a min can be drawn, and that these can be fitted directly to the incoming mains without any other steps needing to be taken.

[Jeremy Harris]

The easy way to check is to look at whether or not a pump set has WRAS approval for direct connection to the water main.  That will be readily available from the manufacturer on request.

 

As above, the flow rate is neither here nor there, as it's the pressure in the main that is the critical factor.  Because all water mains have leaks somewhere in the system, it's very important that the pressure in them is never allowed to reduce to the point where contamination could be drawn in, hence the reason for not allowing direct connection of a pump set.  In theory it should be possible to get a pump set WRAS approved with some sort of clever control system on the suction side, so as to ensure that the pressure cannot drop below the lower allowed threshold, but I'm not aware of any pump set that has such a feature (and I've looked at the specs of lots of pump sets, as we have a pumped water system).

[Ferdinand]

More information.

 

I had a detailed conversation with the Bathroom / Kitchen Fitter over coffee yesterday.

 

He suggests an in line suitable-for-purpose, which is fine. But he has not fitted one before - not necessarily an issue, but means I need to keep a weather I on the process. Do I need to specifiy anything etc. Is there a brand of "solid, reliable" pump which won't be horribly expensive.

 

Is it sensible to buy a spare at the same time? Can anyone recommend a source?

 

Questions:

 

1 - Am I better going to an accumulator? It would be whole house as disentangling the plumbing to 2 bathrooms at opposite ends could be complex. That should not be too much of an issue for usage, and would be quite nice for eg washing up. Central heating is a sealed system. The main time where we have a problem is morning showers, so it would have plenty of time to top up.

 

I am guestimating a 400l-500l jobbie, since my peak demand is likely to be a couple of showers plus a bath plus odds'n'sods.

 

2 - Are there regs and regular maintanance for an accumulator? Or are the FAF (fit and forget)?

 

Cheers

 

Ferdinand

 

Edited April 14, 2019 by Ferdinand

[Jeremy Harris]

There aren't any regs for an accumulator, and they are almost fit and forget.  They can lose precharge pressure over time, and the internal bladder may need replacement after a decade or so, but it's pretty easy to keep an eye on the pre-charge pressure from time to time and make sure things are OK (no different to checking tyre pressure, as they use the same valve).