[R] series of densities

[Troels Ring]

Dear friends
I'm trying to plot in silico derived values of 3 types of 
buffer-capacities  over pH values and want densities of the three types 
together at each pH with the pH values on the abscissa.

I have generated some data

set.seed(2345)
pHs <- c(7.2,7.4,7.6)
pH <- rep(pHs,each=30)
BC <- rep(rep(c(20,10,10),each=10),3)+rnorm(90,0,5)
type <- rep(rep(c("TOT","NC","CA"),each=10),3)

ddd <- data.frame(pH,BC,type)

GG <- ggplot()
for (i in 1:3) {
   dd <- ddd[ddd$pH==pHs[i],]
   GG <- GG + geom_density(data=dd,aes(x=BC,fill=type),alpha=0.1)
}
GG

but here I only get all pH values  plotted together whereas I want 3 
series in the vertical direction at the three pH values.

I wonder how this could be done?

All best wishes

Troels Ring, MD
Aalborg, Denmark

PS: Windows 10,

R version 4.0.5 (2021-03-31