Combi Low Flow Rate

[sat312]

Hi,

Firstly, I do apologise if this topic has been raised in other posts but sometimes it's hard to follow posts especially when they get hijacked and the topic goes off at a tangent.

So I hope someone can provide me with some guidance on how I can improve the water flow and pressure to my shower.

My story is that I just had a Worcester Greenstar 34CDi Combi installed. To improve water flow I had replaced the lead pipe to the main stop cock at the boundary. The flow rate I have now is approx. 10l/min at a static 1.5 bar. This flow was true at both the shower head and kitchen tap. Calculated separately.

I tested on a few other times during the same day and I found that at one time the pressure was 1.8 bar but the flow rate at my shower dropped.

Does the boiler cap flow?

In any case what I wanted was to have a system that would give me a good shower experience. With my current system I cannot get a decent shower during the morning or when I return from work.

Prior to this I had a conventional y-plan system which served me well.

From various posts I am concluding that to increase my flow rate I can install a booster pump or break tank or a accumulator or accumulator+pump.

Due to cost I was considering a small accumulator with a pump to recharge quickly. Can someone advise what setup I should have to have around 10 min shower x 4 people, one after another but have min. 12l/min flow?

I do apologise for the long post.

 

[Agile]

Do you mean your cold flow rate is a dynamic 10 li/min @ 1.0 Bar?

Or do you mean a static pressure of 1.0 Bar and an OPEN pipe flow rate of 10 li/min ( which is not enough for a combi.

You need a dynamic flow rate of AT LEAST 10 li/min @ 1.0 Bar!

Didn't the boiler installer twll you that was not enough? Or was he a nupty?

Tony

 

[petertheplumber12]

Your boiler can deliver 13 litrs/min with a temp rise of 35degC in other words if the incoming water temp is 8-10degC then at 13litrs/min it should be 43-45degsC it doesn't matter what the pressure is that should come out of the tap at that rate and that temp. You cannot talk about flow with a combi without talking about temp as well. If the cold water tap is less than 13litrs/min then you need to fix that 1st and if you had lead coming to the house and now it is 20mm plastic then your problem is a restriction in the house, if it is that low the flow rate then ask the water board to check flow outside, they will do it for nothing.

 

[sat312]

Agile,

The plumber stated that boiler and new mains plastic pipe would be enough to satisfy my requirements. So I took his word. Well pressure has gone up but flow is still not quite there.

My original requirement was to replace my aging potterton profile 80E and vented tank with new boiler+fast recovery cylinder. I was told new boilers are great and with mains upgrade I should get better pressure at the shower then my shower pump.

One expensive mistake but not much I can do now except try to plug the leaks in my wallet

With regards to pressure, I calculated static pressure of 1.5 Bar and an open pipe flow of 10l/min but pressure fluctuates throughout the day. At one time I had 1.8 bar but my open pipe flow dropped to 7l/min. I could not figure this out.

 

[petertheplumber12]

If flow is less than 10litrs/min I think it is, then the water board have to be told and they check it in case there is a leak underground affecting flow rates.

 

[Tom1981]

A combi boiler doesn't have a wicked flow rate. What's the flow rate of the cold? You've mentioned rates, but not if it's hot or cold. The boiler does have a flow restriction it it, but if the incoming flow is poor then the combi will be worse.

I must say, if you wanted a really good flow rate I would have recommended a unvented cylinder with a new boiler to heat it. These are mains pressure hot water delivery, expensive but great for baths and showers.

 

[sat312]

Peter,

I agree that temp should be part of the equation but I was looking at just the amount of water distributed at the shower head, even if it's luke warm.

As far as lead pipe is concerned, I phoned up Affinity Water and advised that I have removed lead pipe from my property and I would like to have the remainder removed. They said that they will send engineer around to test pressure and lead content. If both are within legal limits i.e. =>1 bar then they will not do anything but I can have it removed for a cost which I would have to pay.

The current open flow rate is 10l/min so if Affinity Water don't remove the lead pipe and change stop cock then I have to look at alternatives. Hence my original question about accumulator+pump?

 

[ALEC1]

make sure the shower head is for low pressure... cheap ones can be bought for less than a fiver...

 

[sat312]

Tom1981,

Flow rate is cold water at kitchen sink and I did the same test on shower head. Shower has thermostatic mixer but results are same even when set to 38 degrees.

And I totally agree with you on unvented system as I had this before and it was perfect. 13 years with no problems at all. It was just taking too long to heat tank.

What can I say, I listened to the plumber

So any ideas on what I can do to increase flow to at least 12l/min other then my water company putting in a big pipe?

Not sure if this will happen but I need to look at alternatives.

 

[muggles]

Get one of these fitted to your mains
http://www.plumb-warehouse.co.uk/sh...umbWarehouse&gclid=CK_7jZyW2rYCFZLKtAodGWoAsw