supply pipe to house 15mm

[richardbcampbel]

Hi, have a new house and am doing up the bathroom but the supply pipe feeding the house is 15mm and then splits off to the combi boiler and cold water pipes in the bathroom, the problem is when you run a hot water tap or cold when you turn on the other the flow to both is restricted.Is this a result of both being fed from the 15mm pipe which runs under the house which has concrete floors and what would be a solution as im putting in a mixer shower and can see this being problematic, thanks.

 

[Rybo_1]

As you have a combi boiler it is the norm to notice a drop in flow when having more then one tap running. There's no easy solution to this. I have fitted a booster pump before the help with the flow drop and this could be a costly, but useful outlay if you wanted balanced taps

 

[lame plumber]

35mm mdpe

 

[Chris F]

Yes mate,as above,15mm supply is a tad small.

 

[richardbcampbel]

since i cant very well dig up my entire floor would a possible solution be to take a 22mm of the main then splitting to 2 15mm one being the current supply and one 15mm of it run round the house and give the combi its own supply and cap off the old combi supply, thanks again.

 

[AWheating]

Pointless forking out for larger sized pipework if your mains not going to give any more out.

 

[Ray Stafford]

You need to check what the incoming main size is. Thats the blue (if the service is relatively modern) or black (if its older) plastic supply pipe coming from the street.

Lets assume its blue. If its 20mm, then there is no point in doing anything inside your house. The ID of 20mm blue poly is about the same as 15mm copper. If its 25mm then at least you have something to work with, and its worth upgrading the internal pipe work - but make sure that you change any isolating valves for full bore ones. No point in upgrading the pipework, and then introducing throttled valves.

 

[richardbcampbel]

would it not give more out though if the pipe coming off the water main was 22mm being split into two 15mm pipes with a seperate supply for cold and the combi than one 15mm supplying both?

 

[Ermintrude]

Splitting half a turd still gives you one turd halved

 

[Reg Man]

Splitting half a turd still gives you one turd halved

Nice analogy

 

[wetdrip]

Nice analogy

I too, thought so.

 

[AWheating]

A dedicated 15mm cold to the boiler as the first connection after the stop tap may improve the hot water flow when a cold fixture is used at the same time. But it may not be a great difference.

 

[stratplus]

A dedicated 15mm cold to the boiler as the first connection after the stop tap may improve the hot water flow when a cold fixture is used at the same time. But it may not be a great difference.

Pipers favourite! !

 

[townfanjon]

Splitting half a turd still gives you one turd halved

classic, lol

 

[Masood]

would it not give more out though if the pipe coming off the water main was 22mm being split into two 15mm pipes with a seperate supply for cold and the combi than one 15mm supplying both?

Depends on where the restriction is. As Ray has said, if you have a poor incoming mains, nothing you do inside the house will make a great deal of difference. If your incoming mains is a decent sized pipe, good flow rate and pressure, then look at internal pipework. Start at the source then work downstream. Or think about a break tank and pump setup.

Digging up floors is sometime a necessary evil. At least it's only concrete and you are currently refurbishing. Some people have to take up fitted hardwood or tiled flooring AFTER the house is beautifully finished...