Worth putting full-bore isolators on shower

[kjacko]

Hi all, i've been advised by more than one person to use full-bore 15mm isolators for our new shower valve fittings.
Question is, i've not used full-bore isolators elsewhere, in particular on the same pipe about 3m prior to the shower isolater, so will the shower flow still suffer or is there a certain distance after a half-bore isolator when the flow hits full speed again?
Does that make any sense?

 

[Dan Robinson]

You've done a half a7sed job so far - might as finish off in the same vain .

 

[Phill Peck]

If there is a valve 3 metres away are u sure u need another one

 

[Burnerman]

Full bore isolators all the way!
John

 

[HERTS P&D]

If there is a valve 3 metres away are u sure u need another one

'Just in-case'......................there is a leak!

 

[Charnwood]

It might be what the plumber had to hand when joining the 3 metre length of pipe. Easier than going to the van to fetch a coupler.

 

[Boilerman2]

As a Service Engineer I can tell you that you can NEVER have enough valves on a system!! FULL BORE valves offer little or no restiction to water flow so should always be used

 

[kjacko]

Thanks for those who offered constructive advice.

I did ask a couple of plumbers and they said full bore weren't really needed, but to use full bore on the shower valves.
The pressure and flow of water is pretty damned good anywhere in the house to be honest.
My main question was that once a semi bore isolator is installed somewhere does it mean that the flow after that isolator will be reduced?
Surely after a certain distance it builds up again, the way water through a damn maintains a heavy flow further downstream?

To answer some of the snidier posts, i'm doing it all myself and have loads of isolators but no couplers, so i used them. But i only bought 2 full-bores for the shower according to the advice i got.
We're on a combi boiler, does that make a difference?
I'll reiterate that the flow and pressure is really good already, the existing bath and sink that have been fitted with semi-bore isolators have no problems at all in fact the monoblock sink tap seems a little too powerful.

 

[Burnerman]

With restricted isolators, the pressure remains the same but the flow of water is reduced - which may or may not have a bearing on what you are going to install.
If your shower was a gravity one, then full bore stuff is vital - with a combi the reducer type could may well be fine.
I'd still fit full bore stuff though (they are only slightly bigger in diameter than the usual isolators)......so there's nothing to worry about later.
Some reducing isolators can also produce some water noise.
Good luck with your project!
John

 

[kjacko]

Thanks Burnerman. Due to the advice i received and the crazy costs of full bore isolators compared to semi bore i did buy a bulk pack of semi bore ones.

The shower valve is this one:
http://www.bathstore.com/products/metro-exposed-thermostatic-shower-valve-1689.html

 

[kjacko]

Seeing as this is my thread i'm gonna go off at a tangent slightly and ask another question.

The shower linked to in my last post has the following fitting instructions
http://www.bathstore.com/files/KERRIDGE/20007013010/INSTALL.pdf

My problem is that i'm using wallplate elbows, BUT the 's' connectors of the shower valve (see link above) don't screw into the elbows to the same amount, ie. one screws in and tightens at about the 3'o'clock angle, the other at about the 7'o'clock. Which obviously means that due to the shape of the 'S' connectors they will be at different heights.
If i looseon one off to match the other then surely it won't be watertight anymore, even with loads of ptfe around it.

Any advice on this please?

 

[gasmataz]

If you have good pressure and flow rate I doubt you will notice any difference from full bore or semi. Best of luck

 

[SimonH2]

My main question was that once a semi bore isolator is installed somewhere does it mean that the flow after that isolator will be reduced?
Surely after a certain distance it builds up again, the way water through a damn maintains a heavy flow further downstream?

The flow rate along the pipe will be the same at all points along the pipe (unless you have a leak or a tee off to another outlet. Think about it, for the flow rate to vary along the pipe, the quantity of water going along it must be varying, and water isn't going to spontaneously appear or disappear.

Also, a half-bore valve (or any other fitting) does not restrict the flow rate - you can get the same flow rate by altering other parameters (within limits). What it does is introduce a restriction. When you put a flow of fluid through a restriction then your get a pressure difference (aka pressure drop) - even a length of pipe produces some pressure drop when the fluid is moving.

It is the overall pressure difference, in relation to the flow restrictions, which sets the flow rate. Your pressure difference is effectively that between your mains supply and atmosphere. The overall restriction is really the some off all the restrictions from the supply to where the water comes out into clear air - your mains supply pipe, main stopcock, all the internal pluming with lengths of pipe with fittings, various service/isolator valves, the heat exchange (assuming a combi), your shower valve, the shower hose, and the shower head. For an open vented DHW cylinder, you've got the head of water in the header tank as your overall pressure difference, and then all the plumbing and fittings between there and the nozzles on the shower head as your restrictions.

If you increase the total restriction, then the same pressure will give you less flow. So yes, adding a small orifice in a pipe run will reduce the flow rate. it doesn't do this my magically sensing and controlling the flow rate, it does it by increasing the resistance to flow - the flow rate will drop until the pressure drop in the larger resistance is reduced to match the available pressure.

Also, it doesn't matter (again within some limits, and for non-compressible fluids like water) where you put the restrictions. Putting a small bore service valve at the start of a long pipe run will create the same additional resistance as if you put it at the end of the pipe run.

 

[Charnwood]

If i looseon one off to match the other then surely it won't be watertight anymore, even with loads of ptfe around it.

Forget polytetrafluoroethylene tape, use Loctite 55. You can 'back off' a threaded joint without fear of it leaking.

Full bore isos may be twice the price of standard cheapos, but may well cause half the hassle, depending on your circumstances.
Cheapos make good dual-purpose valves; flow restrictor/isolating valve.
We sell some cheapos which are barely 10mm bore. Sell like hotcakes compared to full bore or WRAS approved ones.

 

[kjacko]

If i looseon one off to match the other then surely it won't be watertight anymore, even with loads of ptfe around it.

Forget polytetrafluoroethylene tape, use Loctite 55. You can 'back off' a threaded joint without fear of it leaking.

This sounds interesting, could you expand on this please?
Are you saying to essentially use glue instead of ptfe tape?
When you say you can back off a threaded joint, what do you mean?

I was having nightmares of how i was going to achieve this because if i don't have the valves tightened to exactly the same angle they will sit at different heights and more importantly be further apart or closer together than they are supposed to be (150mm centres), due to their offset shape.