New MDFE feed

[trevorbayliss]

We have switched from the old lead to 25mm MDFE pipe and it went live last week.

All good, but there is no uplift in the pressure. Is this the norm ? I was thinking we may get an increase in the pressure.

We are getting 50L per min into the stop tap, but it seems this really slows down the flow as it goes from 25mm to 15mm.

 

[magicmushroom666]

A larger pipe diameter would mean more flow, nothing to do with pressure you'd receive, that comes from a pump or a difference in height.

 

[trevorbayliss]

Ok, so the flow / pressure is the same as before.

I did initially think a 32mm feed might be the way to go based on what some folk were saying about better pressure etc.

Looking at it now, it seems irrelevant what pressure/flow the water comes up the garden at. Everyone is reducing down to 15mm as soon as it enters the building and this seems to be the big factor in the water pressure/ flow.

 

[Gossamer]

Ok, so the flow / pressure is the same as before.

I did initially think a 32mm feed might be the way to go based on what some folk were saying about better pressure etc.

Looking at it now, it seems irrelevant what pressure/flow the water comes up the garden at. Everyone is reducing down to 15mm as soon as it enters the building and this seems to be the big factor in the water pressure/ flow.

I'll be doing this soon. Is the pressure at the taps better?

 

[trevorbayliss]

My first post is asking why the pressure hasn't gone up, so no it makes no difference. Everything seems the same with the 25mm new feed as the old lead feed which will be a narrower pipe.

I think the fact that all water comes into the house at 15mm is the reason.

Our pressure is fine though and i didn't change the lead for this reason, so just expecting a little bonus increase which hasn't happened.

 

[JohnD]

Ok, so the flow / pressure is the same as before.

flow and pressure are not the same.

50lpm available to the internal stopcock is very good.

If the flow is poor, take a look at your incoming stopcock, and any service valves, and especially ballofix valves or flexible tap connectors, which are very restricting. You might profit from at least fitting 22mm copper between your internal stopcock, and the hot and cold 15mm pipes that join onto the incoming pipe, and a 25/22mm stopcock.

Do you have a combi boiler, or an unvented cylinder? Increasing the pipe size to it is likely to improve your hot flow, especially if you change any valves to full-bore.

 

[trevorbayliss]

The cold feed now comes in at the rear of the house and fits onto the cold feed tee'ing into the washing machine. After this i have a check valve which is compression and then another about another 70cm further up the piping. All this is in the big cupboard downstairs which is a mini laundry. I haven't checked these valves, but i wonder if these could be a problem ? They are older and required a flat headed screwdriver to move them. I can get a photo if needed.

My stop cock is brand new so i can't see that being a problem.

We have a combi. No difference in shower experience. It wasn't bad before, just no different.

 

[JohnD]

can you show us a pic of these valves?

What size is the stopcock?

 

[trevorbayliss]

Pics of:

1) the stop cock

2) Where the 15mm of new plastic water feed connects to the older copper work.

3) The isolator just along from the T for the washing machine

4) Another isolator a little further along from the first isolator

 

[JohnD]

the appliance isolators don't matter, all they do is restrict flow into the appliance.

I don't understand the purpose of the check valves (I am not a plumber). Are they intended to prevent backflow into the main, for example if a fire engine or other pump creates suction in the main?

I've only used such things on the supply to a garden hose, where the end of the hose might be in a puddle or pond or otherwise unclean.

I imagine they constrict the flow.

If they are just isolation valves, you can get a full-bore one with a larger waterway, that will not constrict flow.

This is a good brand
https://www.screwfix.com/p/pegler-ball-valve-blue-15mm/11085
Observe the "fatter" body which allows a larger ball with a larger aperture.

 

[trevorbayliss]

The copper plumbing was in when we got the house. I just thought they were valves to isolate that section, but the guy fitted 2. Maybe he got so far with a run and then continued and for some reason fitted another one.

Really i should just look at removing these valves if i can and soldering some new copper to the old.

I will look into this when i have some time. Thanks for the link

 

[Madrab]

I don't understand the purpose of the check valves (I am not a plumber). Are they intended to prevent backflow into the main, for example if a fire engine or other pump creates suction in the main?

It is to protect the mains yes if there is a drop in pressure on the upstream side. Part of the regs.

Everyone is reducing down to 15mm as soon as it enters the building

Not necessarily true, a lot of new builds have 22mm for its main distribution pipe. All depends on size of property, etc.

Those ISO valves look as if they are full bore. The bigger issue is the drop to 15mm. Pressure won't be affected/altered unless the mains is hiked up, neither will the flow as a 15mm pipe wil only pass a certain amount of water at a given pressure per min. Multiple bends will also slow the flow.

 

[OvertonPlumber]

None of that complies with current water regulations.

 

[trevorbayliss]

Why doesn't it comply ? What do i add to make it comply.

Should i remove those check valves then or leave them in ? I don't really need them.

The old lead came in at the front of the house and up into the downstairs toilet. I am doing an extension so i thought i would renew the old lead as it is free at connection. All i needed to do was the digging up the drive which i am also renewing. Hence i have done it.

So the pipe comes in at the back and is T'ing into the end of the old pipe run (where the washing machine sits). Everything is working fine, but i was expecting a little uplift in pressure.

 

[Madrab]

By the looks of it those 2 valves in your pics aren't check valves, they are FB isolation valves.

Water regs dictate there would normally be a check valve just after the mains stop tap, then a drain valve but would you be shot for not having them, probably not.

Pressure would not be altered by changing the supply pipe, unless the mains pressure was increased by the supplier. You confusing that with seeing an uplift in flow. Increased pipe diameter increases flow at a given pressure, it does not increase the pressure itself but as your system is all 15mm with elbows in abundance then that may be why the flow hasn't increased.