On 2015-06-26, Chris Hogg wrote:

We have exactly as per your diagram. TW's idea of tees with screw caps
for cleaning would seem a useful improvement, provided they don't
leak. Ours haven't needed cleaning in the 15 years we've been here.

If ours leak, it will be in the dirt-bottomed crawl space under the
kitchen (which is accessible --- not pleasantly, but crawlable).