How can I get it up

[MARMITE]

Done several dark beers recently and my PH at start of boil has been about 4.9-5.0 I have been increasing my calcium carbonate until my latest brew a Fullers porter clone had 1 tsp on the back of a alkalinity in my tap water of 116.How much more dare I add to get the PH up a bit or is there anything else I can do

[steve_flack]

What a nice problem to have

4.9-5.0 doesn't sound too bad to me but there's nothing to be harmed by adding chalk to the mash tun (as it will do bugger all anywhere else). More calcium never hurt anything.

[MARMITE]

Thanks Steve. I did add my 1tsp to the mash tun and mixed it with the grist. How much more do you think I dare put in?

[steve_flack]

Try it empirically. Add half a teaspoon (or maybe a whole one) more and stir it in, see what pH you get. As I said, I don't see a huge problem with your mash pH as it is. It's not optimal but it's not a disaster. I've brewed nice stouts with mash pH's like that.