Will an accumulator solve this issue?

[LordFrederickIII]

Current setup is a OSO 330l unvented cylinder which also supplies four bathrooms. The house is old and big, with the water having to flow that bit higher. There is also a Grundfos Hot Water Circulator Pump attached to the pipe work. The flow rate isn't great so we're looking to see what we can do to improve the situation.

Static pressure is approx 5.5 bar
Flow rate at cold taps is 7.5l/min
Flow rate at hot taps is 3.6/min (this is probably due to the strainer needing a good clean)

With three taps running static pressure falls to 3 bar and the cold flow is negligible from the three taps.

The options as we understand them would be to either boost the incoming supply or add an accumulator. Attached is a picture of the stop cock and piping which we believe is a candidate for an upgrade. However, what we don't know is how much the water board will charge to update the pipe work into the house.

The other option is an accumulator. Would that improve the flow rate we're currently getting, or should we be looking at another solution?

Thanks

 

[Madrab]

With 3 taps running then any mains pressure reading would be dynamic, not static, but hey, we know what you mean

Sounds like you have a flow restriction somewhere that would need to be traced. Even with 15mm the flow should be better than that. All that being said though, ideally that cold mains would be 25mm.
Is the flow coming off a balanced feed or straight from the mains?

 

[simond]

The answer to your question regarding the accumulator is Yes.

However, it is worth investigating the water supply pipe upgrade cost (but only if your water co will guarantee a flow rate) and also checking the strainer in the unvented water group.

Also, sometimes the pressure reducing valve can fail giving the problems you describe.

 

[LordFrederickIII]

Is the flow coming off a balanced feed or straight from the mains?

There's a T junction coming off the mains pipe which then flows into the cylinder and the other part of the mains pipe continues around the house

The answer to your question regarding the accumulator is Yes.

Also, sometimes the pressure reducing valve can fail giving the problems you describe.

Ordered a new PRV this morning on the off chance that it might be related to the problem

Will the accumulator significantly improve the flow or is the limiting factor the pipe work?

 

[simond]

The narrow bore restrictive pipework is assumed to be on the supply pipe from the road?
Assuming the pipework within the dwelling is suitably sized the accumulator will make a big difference.

 

[LordFrederickIII]

Just took a look and the internal water pipework looks to be 1/2 inch

The radiator pipework looks to be 1 inch

 

[Agile]

If you have a dynamic pressure of 3 bar the you should get a good flow rate.

Few people get a static pressure that high.

In much of London its lucky to get 1.5 bar at ground level!

Tony

 

[Agile]

An accumulator is the last think to be considering, although with a static pressure it would work fairly well.

Tony

 

[LordFrederickIII]

Ok, so before I go ahead and order an accumulator, I'll get the new PRV fitted and see what difference that makes.

 

[Madrab]

I'd be tempted to pull off the outlet side of the mains stop cock and attach a pipe to measure the flow and see if you are getting at least 12L/Min, which your water supplier would normally be supplying as a min.
Are you in a hard water area?

 

[LordFrederickIII]

I'd be tempted to pull off the outlet side of the mains stop cock and attach a pipe to measure the flow and see if you are getting at least 12L/Min, which your water supplier would normally be supplying as a min.
Are you in a hard water area?

Apparently we are in a hard water area. I'd have said mildly hard

 

[Agile]

You don't just "go and order an accumulator".

You need to measure the existing supply parameters and design an accumulator installation.

You are unlikely to need one anyway.

Upgrading the supply pipe size would be the first choice before any accumulator.

I doubt that you understand how an accumulator works or what it can and cannot do!

Tony

 

[LordFrederickIII]

I agree, I don't understand the full workings of an accumulator - hence why I am asking on this forum.

I'll be doing the cheapest option first, which is to replace the PRV and see how that affects the outcome. This video shows the issue and possible resolution to the hot water flow:

 

[simond]

I would agree that you don't just go ahead and order an accumulator, but then I would also disagree that the first thing you would do is upsize the supply pipe.

We've fitted many an accumulator for customers who have read the various forum jockey's ramblings and invested in a bigger supply pipe only to get a hardly discernible improvement. They've wasted a lot of money.

In the case of this post I've recommended looking into restrictions in the supply first, because with a static of 5bar there is clearly a good chance of getting an improvement in flow rate. But it gives people the wrong idea to say 'always upgrade the mains pipe first' because, frankly, it is supposition - people then read these statements and take them as gospel.

 

[Dan Robinson]

15mm incoming supply @ 3 ish bar.