Poor water flow rates with 2bar pressure, is it all down to having lead pipes?

[Pinkje]

Since we moved in 2 months ago I have been disappointed with the power of our new shower. I have measured the water flow rate at the kitchen tap (6litres/minute), the en-suite shower (6l/m) and the bath (also 6l/min).

The water flow rate at the outside tap is 18l/m - and this is with the same source of water - the supply pipe t's off outside, one return into the house, the other to the outside tap.

My builder measured the water pressure today, inside water pressure is 2bar - outside 2.15.

On the Hansgrohe shower documents, it suggests with a 2 bar incoming pressure we should be able to get 18l/minute which would be wonderful.

Now I know we have a lead supply pipe and we will get this replaced, but will that be enough to increase the water flow? (can't see how as the water flow outside is already quite good).

Any advice? Thanks.

PS - all indoor plumbing has been replaced with 22mm and 15mm poly-something pipes.

Is the stop tap on the waterpipe entering your house fully open?

If it not fully open it will restrict the flow.

It is usually under the sink but you need to find it and check.

I say this as it happened to us as we had not realised the plumber had not reopened the tap properly.

yes the internal stop cock is definitely fully open but I wonder if the external one is.......I'm sure there is a stopcock after the T junction outside, i will look tomorrow, thanks.

Would the pressure reading be the same regardless of whether the stopcock was fully open or not?

pressure is not the same as flow.

if you get 18lpm at the outside tap but not inside, something is constricting the flow. Possibly flashy stylish continental taps; possibly small pipes, possibly the stopcock; possibly ballofix type service valves and flexible braided tap connectors.

Measure the flow at your washing machine tap.

Thank you PJ. I have had the pressure measured at the washing machine tap, it is exactly 2 bar.

The pipes have all been replaced with 22mm until they get to the bathroom fittings, then they reduce to 15mm.

We have hansgrohe showers and taps and I have seen some braided tap connectors (think they all are). Could that explain the difference?

I also wonder about a blockage somewhere outside after the T but before the water reaches inside, so in the new pipe that has just been fitted, would that be possible? And could that explain the dirt/sediment in the toilet cisterns?

I would love to find a solution that doesn't involve bringing in another plumber.

Measure the flow at your washing machine tap.

Not the pressure.

Okay, flow, not pressure; how would I do that?

squirt it into a bucket, time it, calculate litres per minute.

It will be easier if you have a hose that fits the thread on the valve. Some garden hose connectors fit, or a spare appliance hose will fit
(both ends)

Ok, thanks. I'll see if I can try that later - I'll post results if I can.

We have just had a Bristan thermostatic shower fitted and have this problem too. Flow rate seems fine in main bathroom, kitchen sink etc but only 8l per minute out of the fixed shower rose, not awful but Bristan say it should be more like 19l per minute - Am wondering why but have booked a service of our unvented (megaflo)system in case it Isn't the right pressure?

look for restrictions like these. They are very common, because they make it easier to install or repair.

service valve
The hole in the ball is tiny, and restricts flow. Pegler is a good brand, but you can get cheap ones for 99p or so that are very prone to leak for no apparent reason.

this is a full-bore Pegler. Observe how much fatter it is in the middle. It does not restrict flow. The lever can be removed if necessary.

this is a flexible connector. The pipe inside the braid is much smaller, and it has a ball-type valve as well. You can get a 22mm size (intended for bath taps) which is much less constricting. It can be adapted to fit 15mm copper pipe and half-inch basin or shower stems.

PigletJohn, we have all three of those throughout our plumbing. Is that what the problem is?

could well be. It will reduce the flow. The reason for testing at the washing machine valve is that it (probably) does not have one of these restrictions, and is probably quite close to the incoming supply.

It doesn't matter on most taps, but on showers it does; and on bath taps (if you don't have a combi) because it takes longer to fill the bath.

I've just measured the flow at the washing machine. It is 12litres/minute so double that of the kitchen tap.

I also retested the shower flow (downstairs shower, nearest the hot water tank), it was 7.25 l/m then when I removed the shower head the flow increased to 10l/m.

That still seems low if the pressure is 2bar though. What do you think?

you said you had 18lpm at the outside tap, so I reckon it is multiple restrictions cutting down the flow.

Even the washing machine tap is less than the outside tap, and I expected it to get the best flow in the house. Have a good squint along all the pipes and see how many restrictions you can find.

Flow will reduce according to the length of pipe, and even the number of elbows and tees the water has to push past, but I think you will get an improvement by upping the size of your valves.

The shower mixer, and the head, will themselves restrict flow, so you need to give them the best chance you can.

BTW the pressure coming out of the needle of a hypodermic syringe is at least a hundred time greater than that coming out of your bath tap, but the flow is tiny, because the pipe (needle) is very very small. For good flow, you need unrestricted pipes, not just high pressure. The bath taps will benefit from 22mm pipes, which I think you said you had.

Thank you.

So, in your opinion would it be a good idea to replace the outside lead with plastic (think I already know the answer)?

yes, of course. The old lead pipe is probably half-inch internal diameter, and might be squashed in places. Change it to at least 25mm, and preferably 32mm (the extra cost is insignificant) and have full-size stop-cocks fitted at every point (some plumbers may want to fit smaller stopcocks, because there is a price difference)

I would also change any service valves to full-bore Pegler ones (again, there is a price difference)

If you have flexible connectors on your taps, they are very convenient. However if the tap concerned annoys you by its poor flow (especially a bath filler or shower) consider changing to a 22mm connector, with adaptor, or to plain pipe. Bending copper pipe takes some skill and time. You might still be able to get flexible copper tap connectors, which are made of full-size pipe.